Most divisors are looked up in tables based on your age. Others are calculated based on last year’s divisor. Some particularly unfortunate cases have distribution deadlines rather than divisors at all.
We recommend that you fund your Health Savings Account (HSA) to the maximum limit each year and that you keep funding it to the maximum as long as you can no matter how much money you have in the account.
Determining what constituted a safe withdrawal rate was one of the first questions I tackled. After a year and a half of study on the question, I had realized the inadequacy of the 4% rule and found a methodology which provides more useful when advising clients.