The way that I see it, once someone has a method plan that they feel confident in, then they can just exit this world when the time feels right for them, and only the individual knows when that is. I would personally not see it as best to set a specific date for ctb far in advance as something could happen to potentially interfere with plans to die as after all, life is uncertain and unpredictable, I would see it as best to exit when the time feels right as I said.