Lots of interesting perspectives here.
It's said that creativity starts to decline after around 28. Well I'm 38 and I say you can only do you!
I don't think there's any biological reason for that and indeed a lot of great work by great artist would refute that.....the list is endless, Miles Davis, woody Allen, Steve Martin, Bill Evans. Hell some composers wrote their greatest work in their 80's! No it aint hip hop but it's creativity. i think the brain begins to go into a small decline in your 40's but again, what you might lose in speed and dexterity you make up for in experience. With pop music a lot of groups do indeed write their best stuff in their 20's and by their 30's and 40's are simply re treading old ground, I suspect their are lots of reasons for that, too many drugs, too comfortable, too much money not enough to say. I think as you get older, things get in the way, kids, wives, Life etc. It gets harder to maintain that edge and literal "hunger". You are simply not open to or available to the experiences that came your way in your twenties.
wrote more songs during that 3 year window in my life then all the other years combined, and I'm currently 43. I never came close to that experience again, and though I'm forced to, I don't enjoy working solo.
I would give almost anything to relive one week of my life back then.
....That saddens me a little, get out there and take life by the balls, maybe you can't and you have other responsabilities but if don't then there is nothing stopping you. If you are a fat git get into the gym, get into shape. Throw out your old cd collection, get some pussy etc.........think young and you will be....think old and you will be.
There is to my mind nothing more important to the creative process than experience, pure and simple. Live!!!