I'm 33 and still trying to learn new stuff in the park. I can't honestly say that it's any harder for older people to keep hitting the park and learning new tricks. Anyone who claims that "it's easier for young people" is just making excuses and failing to credit the enthusiasm, determination, skill, and balls that the younger guys who are pulling off the new tricks had to bring to the table.
I will say that hitting the park is different when you are older, though. Here's a few things that have changed for me:
1. No more peer pressure. The good kind. None of the guys that I grew up with hits jumps of any kind anymore, and most gave it up years ago, before rails were even part of the equation.
2. More-injury prone. For some reason, crashes that would have tweaked a knee for a day or two when I was younger are more likely to turn into ligament-snapping season-enders. After sustaining a couple of these, I started to ask "Is it worth the pain, the rehab, and missed days climbing, biking, etc?"
3. Same-injury, different consequences. When I was growing up, health insurance was a given, and an injury meant going to school in a cast. Once you are older and fully on your own, you not only have to think about paying the hospital bill, but what'll happen if the injury knocks you out of work for more than a week. Got short-term disability coverage? Got enough savings to pay for the car, the rent, the groceries, for a while if the disability check doesn't match 100% of your pay? What'd happen to the people that depend on your income if you cripple yourself in the park?
4. Different perspective. Even if you never sustain an injury, you've got enough insurance to pay for life-long veggie-care, and your friends are still getting after it - the odds are good that the way evaluate risks will probably change. Once you hit the mid-20s, it just gets alot tougher to make decisions about risk without fully weighing the consequences.
5. Conditioning. For most people, a natural part of being young is being relatively thin and in-shape. Participating in team-sports at school makes it easier to stay that way. Once youth and team-sports are over, staying fit enough to hit the park without wrecking yourself everytime takes some discipline. Most jobs that pay enough to live on anymore take around 10 hours a day plus commuting time. Toss in some extra obligations, a slowing metabolism, etc and for most people it's a losing battle. Be prepared to work a little harder if you want to avoid a trip to the ortho's office every time you overshoot a landing.
All in all - much easier to claim that you'll hit the parks forever than to actually do it IMO.
