Yes it is age but there are things you can try. It won't come back without a little work.
Kegel Exercises For Men...
It does work. Don't over due it at the start because you will get muscle burn and you don't want it down there, increase reps over time.
Another solution is to go to a Titty Bar and get ground on till you have blue balls, then go see someone within an hour after leaving. Or see a provider that will tease the heck out of you for at least 30 minutes, like someone else said, work you up, then back off till you start to go flaccid...repeat at least 5 times, 10 times is better.