Impermanence of matter and mentality (compared)

It is well known that matter (rupa) arises and ceases slower than nama.

Sixteen or 17 moments of citta arise and cease while one moment of rupa persists. So rupa still only lasts for such a brief time.
There are other differences as well.
This is taken from the Mulatika of the Khanikakatha (i,.e the tika to the Katthuvatthu in the section that refutes the idea that matter and mentality arise and cease simultaneously. (see p. 119-120 of The Theravadan doctrine of momentariness (Wan do Kim).

Regarding the materiality of the earth and so on, arising and ceasing of whatever they are, thus there is a [process] of support (patitthana) by means of the continuity of materiality. For there are no conditions of contiguity (anantara-paccaya) etc. in relation to materiality. If there is a process in terms of material continuity, just as there is in terms of those continuities of immateriality, one may argue that the great earth would synchronise with each mental phenomenon (cittakkhane cittakkhane).

Kyv-mt [C®] 115 6-11: pathaviyddiriipesu kesaiici uppddo kesafci nirodho ti evam patitthanam rupasantatiya hoti. na hi riipanam anantarddipaccaya santi, yehi arupasantatiya viya rupasantatiya pavatti siya ti citte citte mahapathavi santhati ti adi coditam.

Thus we see that rupa has a different type of causes/conditions from nama.

Dispeller of Delusion (commentary to the Vibhanga) p.28-29

  1. (3) “As to limit of extent”. For how long a period does the material last and for how long a period the immaterial? The material is heavy to change and slow to cease; the immaterial is swift (light) to change and quick to cease (cf. Vis 614). While materiality endures, sixteen consciousnesses arise and cease. [261 But that [materiality] ceases together with the seventeenth consciousness. For just as a man, [thinking:] I will knock down a fruit,’ might strike a tree branch with a mallet, and both fruits and leaves are released from their stalks at a single moment, therein the fruits, owing to their own weight, fall first to the ground; the leaves, owing to their lightness, [fall to the ground] afterwards. So indeed, like the time of the releasing of the fruits and the leaves from their stalks at a
    single moment is the appearance at a single moment of the material and the immaterial states at the moment of rebirth-linking. Like the falling first to the ground of the fruits owing to their weight is the arising and ceasing of sixteen consciousnesses while materiality endures. Like the falling to the ground afterwards of the leaves owing to their lightness is the ceasing of materiality together with the seventeenth consciousness.

Chapter 11 - Pacchajata-paccaya

Or The Relation Of Post-existence

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Every posterior consciousness that springs into being, causally relates to the still existing group of prior corporeal qualities born of the Four Origins [1] (kamma, citta, utu, ahara), by way of post-existence, in helping them to develop and thrive. For example, the rainwater that falls every subsequent year renders service by way of post-existence to such vegetation as has grown up in previous years, in promoting its growth and development.

Here, by “every posterior consciousness” are meant all classes of consciousness beginning from the first life-continuum to the final dying-thought. And, by “prior corporeal qualities” are meant all corporeal qualities born of Four Origins starting from the group of material qualities born of kamma, which coexist with the rebirth-conception.

The fifteen states of the life-continuum starting serially from the first life-continuum, which has arisen after the rebirth-conception, causally relate by way of post-existence to the group of material qualities born of kamma, which coexist with the rebirth-conception. As to the rebirth-conception, it cannot be a causal relation by way of post-existence, for it coexists with the group of corporeal qualities born of kamma. Similarly, the sixteenth life-continuum cannot become a causal relation by way of post-existence, for it comes into existence only when that group of material qualities reaches the stage of dissolution. Therefore, these are “the fifteen states of the life-continuum” which causally relate as above.

At the static moment of the rebirth-conception, there spring up two groups of material qualities, born of kamma, and born of temperature; [2] and the same at the arrested moment. But at the nascent moment of the first life-continuum, three groups spring up: that born of kamma, that born of temperature, and that born of mind. When oja (the nutritive essence) of the food eaten, spreads all through the body, the corporeal nutritive essence absorbs the stimulant, and produces a group of material qualities. From that time onward, the groups produced by the Four Origins spring up incessantly, like the flame of a burning lamp. Leaving out the nascent moment, so long as these groups stand at their static stage, every one of the posterior fifteen classes of consciousness renders them help by way of post-existence.

Vuddhivirulhiya means “for the gradual development and progress of the series of corporeal qualities born of the Four Origins.” Therefore, if they, the four kinds of corporeal groups, are repeatedly related by (lit., do repeatedly obtain) the causal relation of post-existence, then they leave behind them, when their physical life-term has expired, a powerful energy–an energy adequate to produce the development, progress and prosperity of the subsequent series of groups.

Nina Van Gorkom:
https://abhidhamma.org/chapter/?chapter_title=Prenascence%20Postnascence-Condition&post_id=769

As to postnascence-condition, pacchajata-paccaya, citta and its accompanying cetasikas support the rūpas of the body which have arisen previously and have not fallen away yet.
Thus, in this way citta conditions these rūpas by way of postnascence-conditioṇ Citta does not cause the arising of the rūpas it conditions by way of postnascence, these rūpas have arisen already prior to the citta; it supports and consolidates these rūpas which are still present, since rūpa lasts as long as seventeen moments of citta.
Citta is postnascence-condition for the previously arisen rūpas of the body which have been produced by the four factors of kamma, citta, temperature and nutrition and which have not fallen away yet. Citta supports and consolidates these rūpas. The paṭisandhicitta cannot be postnascence-condition, since there is no previously arisen rūpa at the first moment of life. At the first moment of life kamma produces rūpas simultaneously with the paṭisandhi-citta, but after that, throughout our life, citta is postnascence-condition for the previously arisen rūpas of the body. The five pairs of sense-cognitions do not produce rūpa, but they condition the previously arisen rūpas of the body by way of postnascence, they consolidate these5. The arūpavara vipākacittas6 which arise in the arūpa-brahma planes cannot be postnascence-condition, since there is no rūpa in those planes.
In the case of base and object which are prenascence-condition, rūpa conditions nama, whereas in the case of postnascence-condition nama conditions rūpa. The teaching of prenascence-condition, purejāta-paccaya, conascence-condition, sahajāta-paccaya, and postnascence-condition, pacchajata-paccaya, reminds us of the intricacy of the relationship between different phenomena. Seeing, for example, is the result of kamma and it is dependent on the previously arisen eye-base which is also produced by kamma. Seeing experiences visible object which has previously arisen but which does not last longer than seventeen moments of citta. There is no self who could arrange for seeing to find its proper base; the eye-base has previously arisen and is already there when seeing arises. There is no self who could fetch visible object at the right moment so that seeing can see it and the other cittas of the eye-door process can also experience it, before it falls away. Visible object arises together in a group of rūpas including the four Great Elements and these condition it by way of dependence-condition, nissāya-paccaya, and by conascence-condition, sahajāta-paccaya, but seeing does not experience the other rūpas which arise together with visible object; it only sees visible object, that is, what appears through eyesense. Several conditions coincide and this makes it possible for seeing to arise at the eye-base and to see visible object. We take the experiences which occur time and again in our daily life for granted, but they all are dependent on several conditions, they are interrelated in different ways. Cittas and the rūpas of the body are interrelated, they need one another. Seeing and all other cittas support and consolidate the rūpas of the body which have already arisen, they condition them by way of post-nascence. The different conditions for the phenomena of our life are operating right at this moment.