LD's are anything but age specific. I'd guess the reason more teenagers are on the site is simply more free time, and more time spent online. Most of the mods are over 20, though, and they're pretty much the most successful LD'ers on the site. I've also managed to teach my three neices to LD, and they're 5, 7 and 10 years old.

Well, anyway. Moving on...
Summer vacation has little to do with increased LD's, at least in my case. During the summer I LD less, because of a lack in a set sleep cycle. I wake up and go back to sleep at odd times, so it's more difficult to LD. Having a strict schedule can actually make it easier to LD! Techniques like WILD and MILD may be a bit harder to work into your schedule, but Reality Checks and DILD are quite easy and require almost no time to perform. If you want more info on these, check the Tutorial Section.

Relaxation and lack of stress is important, though, so finding a meditation method that works for you would definitely be worth the time.

-Tsen