You can sell like, $50k USD worth every week, or in some not-too-distant-future, that would be about 4.3 BTC per month. If you wanted to, you could do multiple withdrawals from several different bitcoin ATMs every day. It could take you several months or years to completely deplete your stash if you had a sizable amount to begin with.
Then you can keep the rest and wait it out. In the mean time, you go play with your money and put it in all sorts of traditional fiat investments just so you have something to do. (or put it into all the crypto ETFs that are about to come out.)
If you believe in bitcoin long term, then you don't really have to rush to withdraw, but of course, no one should be planning on living forever.
Traditional investment strategies presume an ability to withdraw 4% per year without depleting principle value (that can also be considered as 1% per quarter) - so the underlying assumption is that the value of the holdings, on average, are going to gain in value at least 4% per year average to make up for the withdrawal amount. Therefore, in theory, so long as the underlying value of the asset continues to appreciate at least 4% per year, then you can continue your withdrawal plan infinitely at those 1% per quarter levels without depleting the principle.
Therefore, in theory, you are always withdrawing appreciation of the asset rather than the principle. I find no reason that the same practices could not be attempted to be applied to bitcoin holdings because I believe that bitcoin has a decent chance of averaging at least 4% per year in value appreciation. So, therefore, you should be able to apply the same withdrawal of value concepts, once you get to your withdrawal stage of your life.
Of course, if you believe that you are not going to live very long (or you have a time target that you would like to deplete your BTC holdings that is sooner than infinite), then you can plan to withdraw more than 4% per year in order to draw down on the principle as well as the appreciation.
In essence, the more bitcoins that you have accumulated, the larger the amount you will be withdrawing. Let's say, for hypothetical purposes by 2020, you project that you will have a balance of 50 BTC, and you want to begin your withdraw of 1% per quarter at that time for the next 10 years.
Your withdrawal projection would look something like the below table:
Year Quarter Balance Withdrawal amount2021 1 50 0.5
2 49.5 0.495
3 49.005 0.49005
4 48.51495 0.4851495
2022 1 48.0298005 0.480298005
2 47.5495025 0.475495025
3 47.07400747 0.470740075
4 46.6032674 0.466032674
2023 1 46.13723472 0.461372347
2 45.67586237 0.456758624
3 45.21910375 0.452191038
4 44.76691271 0.447669127
2024 1 44.31924359 0.443192436
2 43.87605115 0.438760511
3 43.43729064 0.434372906
4 43.00291773 0.430029177
2025 1 42.57288855 0.425728886
2 42.14715967 0.421471597
3 41.72568807 0.417256881
4 41.30843119 0.413084312
2026 1 40.89534688 0.408953469
2 40.48639341 0.404863934
3 40.08152948 0.400815295
4 39.68071418 0.396807142
2027 1 39.28390704 0.39283907
2 38.89106797 0.38891068
3 38.50215729 0.385021573
4 38.11713572 0.381171357
2028 1 37.73596436 0.377359644
2 37.35860472 0.373586047
3 36.98501867 0.369850187
4 36.61516848 0.366151685
2029 1 36.2490168 0.362490168
2 35.88652663 0.358865266
3 35.52766136 0.355276614
4 35.17238475 0.351723847
2030 1 34.8206609 0.348206609
2 34.47245429 0.344724543
3 34.12772975 0.341277298
4 33.78645245 0.337864525
After 10 years of withdrawals of BTC at 1% per quarter, you still would have a balance of 33.78645245 BTC. Nothing wrong with that, and the same formula to withdraw 1% per quarter will work, no matter what your starting amount.