Thanks jcl, MatPed.

MatPed, you definitely win the prize for being a better student than me!

jcl, thanks for the last clarification! It helps, & I now remember it from years ago...

But now, as then, I struggle with how to transition from blue sky theory to what to do here in the real world. Specifically, how do these 2 reconcile:

1) If in every year the probability is the same for the 2 accounts, then in every year they should be treated the same in terms of withdrawal vs. funds left.

2) But, if in every year they are treated the same, since in each individual year the probability is identical, then because of the lifetime probability difference the older account is more likely to blow up, isn't it? Don't the accounts have to be treated differently somehow to prevent this?

Thanks.