A somewhat philosophical answer, but I think getting old and aging are two different things - you can't help aging, obviously, but you can stop from getting old. I'm only 30, so take my advice for what it's worth, but I've see old people who are 40 and young people who are in their 60's! It really is a state of mind.
When you stop doing the things that young people do (experimenting, learning new things, being creative, living without limits, being a sponge to everything around you) you start to get old, and it's all downhill from there. But that's a choice! You can choose to stop progressing and begin declining, or you can choose to continue doing the things you did when you were younger, granted at a pace more appropriate for your health and state of life.
I think it's important to apply this principle to every aspect of your life - your relationships, physical activity, mental state, music... I think the problem with "old people" is that they feel like they've arrived already, and once you've done that there's only one place to go - down. But if you ask any wise person (regardless of age) they'll tell you that they're still trying to get there, that they haven't arrived yet. That's beautiful and I think something wonderful for me to aim at.
So I say - keep rocking!