What if you have children? You could say they "need the money now" more than you do, and never donate. You could even write a recursive will that defines N=5, and requires your daughter or son, as a condition of inheriting the money, (a) never donate it during their lifetime and (b) write their own will with the exact same text with the only change being N = N-1 (c) donation is only allowed if you are N=0, and only under agreeing to fulfill (a), (b), and (c), do you even get to have the money.