Brian, I agree with you. Fortunately, it's an easily configured value. Unfortunately, it's one of those things where you have to expend time and effort, and lean on the expertise of our generous colleagues here who know so much more about the inner workings of DNN, to find the "fix." (It's not really a fix, but a tweak, to be fair.)
Borrowing from what John just said, though, I do suppose that the short-duration, out-of-the-box 60-minute value might be so short because it's more secure to have a cookie duration of one hour as opposed to something lengthier. If so, I must have missed that memo. <g>
Anyway, I'm just happy to know about the tweak.
Steve