Wouldn't it as well be smart to say that accumulation stage should go on for as long as it is realistic that bitcoin will be in accumulation stage. For example, if I reach my goal and own like 1 BTC, but I see the statistics and know that 2% of the world's population now own BTC, but regulatory bodies are more prone to support BTC development and purchases through government organizations and businesses and it becomes evident that they are not against BTC. They pass laws that allow non-custodial wallets without sending you though cumbersome processes like KYC for every address you own and many other bad things. You realize that BTC has a bright future and you also realize that barely one owns it, would it then be right to stop accumulating when probability is high that BTC accumulation is only about to get started?
I think the right decision would be to then maybe adjust your goal and accumulate further as your estimate is that the market has upside potential. Unless you reached certain limits within your wealth distribution preferences, but stopping when you see it is about to get going should perhaps alter the first decision.
In my own perspective, I think that the ideal time you feels like you have accumulated enough Bitcoin is up too you as an individual, though as humans we always want more, but in life we will definitely get to that level where within us, we can admit that if we stop now, we can as well be ok with what we have, so till we get to that point, I don't see any reason to stop accumulating Bitcoin when it's still very cheap as now.
Lastly, we all know that the stash of Bitcoin in your possession determine how wealthy and profitable you might become in the future, so till you get to that point of satisfaction, you wouldn't even see any reason to stop accumulating Bitcoin, because you aren't satisfy with your current stash of Bitcoin in your possession.
Bitcoin accumulation should be between ones financial capability and shouldn't be a competition to the accumulators against others because it could really put pressure on you as everyone's financial capacity differs. Even if as humans we have that greed instinct to want to gather more and more, as per investment it should be done with proper planning and coordination even when the authorities probably lift most of the restrictions and develop bitcoin friendly policies in the future it still doesn't reduce to nothing the necessity to accumulate strategically even if you seem not to have a limit to the amount you'll want to accumulate.