Overaccumulation is probably going to be a moving target for quite some time. For the sake of putting a plan in place and making sure you understand how to pursue it, having a target is good and important. But it will be more of a snapshot as long as bitcoin has the potential to go many x times up in market capitalization.

If someone has the patience and the discipline to stick to a long term BTC accumulation plan, isn't it more likely that such individual could well end up not having to move to any withdrawal plans at all? This is not a rule of thumb of course as there are still individual circumstances involved, but if someone now begins to build up BTC holdings for the next 10 years straight, maybe 20 years straight, I can imagine that holding those BTC will put that individual into a position of vast flexibility. There is probably still some income from other sources and those BTC holdings could serve as a security guarantee when more costly items have to be purchased, but income from other sources could be used without touching those BTC.

I think in 10 or even 20 years from now, the ecosystem will have evolved further. Higher acceptance, advanced regulatory environment, increased realization that bitcoin is incredibly scarce and not holding any is probably more costly than buying some (fraction), perhaps smart contract based possibilities to make money with BTC holdings, children or relatives who want to keep holdings within the family instead of selling it...

I say this because many people pursue wealth and once they acquired it, something changes in their mindset and the dream about spending it all when the time has come, starts to vanish. Bitcoin will be one of those assets you know you may never get a chance to get it back for the same price. That has an effect on withdrawal decisions for most people.