That shouldn't be the fear the real risk is the 17 to 18 year old high school kids who have bias. Play for Gramps at VTech or play for one of the guys the age of your cool uncle who lets you use his car when a hot date opportunity occurs.
Have to wonder whether, say the Vest and Paterno went head-to-head for a really sought after non-Ohio non-PA guy and who came out on top in the recruiting battle--both programs at the time being easy sells. Was the kid's choice influenced by the head coach and did age impact the decision of who felt comfortable where? Or do head coaches not matter greatly as perhaps the position coaches are more involved and influential in the process.
I'd have to say that the free market has a way of solving that problem. If kids all wanted to play for younger coaches, then younger coaches would universally have better recruiting, and presumably better winning percentages. If they all wanted to play for older, (presumably) wiser coaches, then older coaches would get all the good recruits and winning percentages. The fact that a coach like Paterno was able to continue winning at advanced age is an indication that he was still able to recruit some good athletes, and that he was still able to coach them.
Looking around at the college landscape, I'd have to say that tradition and facilities are probably more important as recruiting factors than age of the coach. I'd say personality of the coach is also important. Finally, I suspect that there are other factors that occasionally factor in, such as the race or religion of a coach, or even his height.
In the end, I don't think you can hope to guess how all the factors will play out, and I think it's a wasted effort to try. I think you just have to end up going back and asking, are they able to win, and able to build the program?
suspect that the height of the coach is a factor as well.