I am thinking that I will meditate for only 30 minutes. Even if, at the 29th minute, I start seeing light or preliminary signs, I will end the session at 30 minutes.
The reason is that I have a very busy schedule. If I meditate for too long, I don’t complete my other tasks, and the cycle of disappointment continues. Meditation feels good, so I want to continue for longer and longer, but I am an ordinary person and I have goals. I want to have a successful life. I do not desire Nibbāna.
Also I think this will stop a craving for greater meditation experience. Or delusion or imagination.
Why do I meditate? Because I want to see nāma-rūpa. I want to know whether kamma is real or not. I want to see cause and effect.