I would probably change "Do you EXPECT to live past 77/81" to "Do you have a reasonable chance to live past 77/81 and want to provide for the largest benefit IN CASE you live past 77/81".
Wordy, yes, but I often see a comment from people who mockingly say that some people "know" they WILL live past 81 (or longer). I don't know when I will die, but in case I live long I want to be better covered. If I don't live that long, I already know I have enough to cover everything. If I develop a terminal illness or have other high risk of dying in the near future, of course I will take SS sooner.