I understand the desire for a buffer. What I don't understand is why that buffer would grow over time (except to keep up with inflation). At age 65 I face all the risks that I will face at age 70, plus a bit more (e.g. being disabled from 65 to 70). Indeed, if anything, as I age, the size of the needed buffer should decrease, not increase. Fewer bad things can happen to me.
George