what is the ideal presta tube valve stem length I have noticed that presta tube valve stems come in various lengths. I always assumed the longer valve stems were to allow the use of deeper aero wheels. Why is it that many wheels in print ads seem to have what I would consider an excessive amount of stem exposed? Is there an advantage or disadvantage to usng a stem that is just long enough?
I think the valve should be as short as possible while still allowing comfortable inflation of the tire.

On the other hand, a longer valve usually "won't hurt", specially if you have more than one bike or your group of fellows use to lend spare tubes to one another during rides (happens a lot to me, but in shcraeder-equiped mountainbikes).

Hope this helps!