Well if you get to the point where your skills playing games have diminished... start making/modding games.
You lead, you organize, you manage, invent, teach.. whatever.
I may not be as good as I was even 4 years ago, but I've definitely shifted from a consumer to a producer role.
You hit 20 and your gaming ability starts falling off at about 8% a year. Least that's how I've seen it.
A lot of burnout is just playing with people that have found that groove, and you get left in the dust. Patience is
shorter, free time is shorter, jerks are in overflowing supply, games cost more, etc. This is partly why cell phone games and the "3 minute game"
has taken off - for all the gamers that still have that itch, but can't regularly play.
I was competing in Blur when it came out, and we were one of the top ten teams in the world. The game flopped, we got out, and decided
to get back in it a year later. Well now everyone and their dog knows a lot of the tricks we figured out to begin with. Some players that have
stuck around have elevated certain skills/play styles to an art form. Where as before we could walk in any game and take over, now it's often
a win-by-a-hair regular event. You don't play regularly... you get sloppy. You get old, your abilities degrade.
Don't worry about it... unless you're going pro and have to perform for your job - it's normal.
There's plenty of gaming clans out there for the 21 and older group too, where brains over brawn (or er... reflexes) win out.
Try stomping around a FPS game with a full team of 24+ age shooter lovers, you "almost" feel sorry for the little twerps, almost.
Play other games... buy/install an old system and visit titles that you never got the chance to play. The "latest and greatest" is often life sucking...