It sounds like you have the potential tax ramifications figured out, and of course, you might be able to withdraw more than $89k per year depending on how you calculate the cost basis, and I am not going to talk about those kinds of accounting and/or tax matters in any kind of detail  

Surely my price based table does account for your ability to cash out at various prices on the way up, however, you could also decide to follow my other sustainable withdrawal table in which bitmover created a website and a thread in which you could figure out a monthly withdrawal rate and then just figure out if your BTC stash exceeds the sustainable withdrawal amounts, which would be time based rather than price based, but there is a price based component in that one too, since it allows advance month withdrawals for better performing months, or reduced monthly allocations for lower performing months and at the same time figuring out your own level of conservativeness/aggressiveness (in terms percentages), and I have taken the liberty to describe 6-10% withdrawal rates as being moderate under a bitcoin system, and if you don't believe my assumptions, then you could choose a more traditional 4% withdrawal rate... which I classify as conservative and even a growth-inclined rate of withdrawal, when it comes to BTC.