Tax Implications: Cashing out Bitcoin is a taxable event in most jurisdictions. Your sustainable withdrawal rate must account for capital gains taxes.
After reaching an over accumulation stage and decides to withdraw using the sustainable withdrawal method, tax payment will be nothing because your portfolio have compounded overtime. Since tax is applicable to your bitcoin withdrawal is the main reason why you should only be buying till you reach your over accumulation target or already old without a discretionary income.
Lifestyle and Flexibility: This strategy assumes a certain level of discipline and the ability to adjust spending if the market enters a prolonged bear phase.
No matter how bear the market will be in future, someone who have been investing into bitcoin for three circles and above will be in profits because the bottom line of the dip in every new circle is always higher that the previous. Also, bitcoin creates a new ATH in every new circle.
However, you are not to be withdrawing from your bitcoin portfolio constantly, but once in a while, to avoid selling too many bitcoin too soon and be left with little portfolio so that you don't regret your actions.