My position on this has changed over the years.

Firstly, to completely sell, my thesis would have to be invalidated and bitcoin proven insecure or capturable by a nation state. So if there is a catastrophic hack or a nation state manages a 51% attack or multiple G7 nation states work together to make bitcoin illegal in their countries I would have to rethink my thesis and decide if I want to continue holding.

Secondly, I used to have a plan to sell half my position in tiers as the price rose. For example sell 10% of position at 100k and another 10% at 200k and so on. This doesn't make sense anymore. There are ways to use bitcoin as collateral to access fiat loans so why would I sell 10% off my position that is going up forever against fiat for fiat when I can just use it as collateral to borrow fiat to achieve liquidity and then have the fiat ice cube melt away the interest it will cost me. Doesn't make sense to sell and pay capital gains tax when you can simply borrow fiat. That being said Bitcoin is volatile, you can't wreck yourself borrowing up to 70% of your position size but you can easily borrow 10-20% and be comfortable.

Finally, there is a scenario where I would sell some (not all) of my bitcoin where my thesis has not been invalidated and that would be if bitcoin's price got extremely removed from where I think current value should be to the upside. Say Balaji's scenario played out and Bitcoin shot up to 1M in the span of 90 days, I definitely would have to consider selling part of my holdings unless I really believed this was the moment fiat was dead and hyperbitcoinization was taking hold. When you look at the gold/weimar marks chart there is extreme volatility for years before marks hyperinflate and gold price goes to the moon. Personally, I think fiat has too entrenched network effect to just go away that quickly so I would have to look at the available facts in a scenario like that and make a decision if I should sell some. (This doesn't imply I would always sell some at 1M, I would much rather have it get there slowly with growing adoption and usage, stabilizing price so I can use as collateral and borrow against it)