How many Bitcoins are enough for a person is a subjective thing. For a person like me who hails from South Asia, 5 Bitcoins will be sufficient but a person living in USA or EU has different criteria of enough Bitcoin.
Once you figure out how much you need, then it is no longer subjective. If you say that you want an income of $20k per year right now, then that would be right around 4-5 bitcoin, like you mentioned, and if you need $80k per year of income starting now, then you need 17.166 BTC and if you have 1 or 2 more BTC, then you have enough of a cushion to feel confident that you are always withdrawing from the overaccumulated amount rather than at any point selling too much BTC too soon.
So the first thing we need to do is to figure out how much bitcoins are sufficient for us? I have done that work, 4 to 5 Bitcoins are good enough for me based on my geography where I live. Likewise everyone of us must figure out how much Bitcoins will be good enough for everyone of us.
But that's correct that once you are having enough Bitcoins then don't go for aggressive accumulation of Bitcoin because all of us are gathering Bitcoins to achieve a specific target and if you already have achieved that target then just relax. It might be a good point for you to start selling some portion of your Bitcoins to enjoy the result of their hard work .
That sounds correct. Once you reached overaccumulation status, you no longer need to accumulate bitcoin, yet you still might have to figure out how you are going to manage your bitcoin so that you don't sell too much too soon.
That's very important stage i.e. once you have that over accumulation status or you have your specific number of Bitcoins, you have to figure out the strategy of how to maintain balance between the number of Bitcoins you hold vs the one you sell. If one can't maintain that balance then very soon he will run out of Bitcoins he accumulated over years.