He should live so long. :-D As pointed out elsewhere, this is an exponential decay so it will never go to zero. Bashing numbers helps me visualize this... Lo

He should live so long. :-D As pointed out elsewhere, this is an exponential decay so it will never go to zero. Bashing numbers helps me visualize this... Looking at (nearly) the worst case, if the trust earns zero interest, he will be draining it by 5% per year, so the principle will be 0.95^y * 22e6 where y is the number of years. If he lives for 40 more years... 0.95^40 * 22e6 = 2.8e6 (13% of the original sum is left). A less drastic case would be earning 4% but paying out 5%, i.e. losing 1% per year. 0.99^40 * 22e6 = 15e6 (67% of the original sum is left). OK, the absolute worst case is he invests the whole amount in subprime mortgages and loses it all. We won't bash those numbers, obviously he is a lot smarter than that.