Thanks for posing the question. It's something I've been thinking about a bit.
Do you go for the guy for whom this could be a career upgrade, but most likely be last destination? Think someone in their 50s with an 8-year deal.
Or do you roll the dice and go with a younger guy and try to sell them on the fact if they turn around the program it will be "their" program ala Paterno at Penn State? The problem with a younger coach, of course, is that it could serve as a stepping-stone.
I wouldn't put age in the quandary department, but the administration needs to be cognizant that a difference in age could present challenges down the road a piece.