Aside from the physical aspect of slowing down, I feel that age does play a role in your involvement in cubing. This can be seen as the dramatic dropoff of fast (sub-10) cubers over the age of 25. This is obviously due to life factors such as getting a full-time job, having responsibilities, raising children, that younger competitors don't really have to deal with.
Our sport (I don't care what people say, I'll call speedcubing a sport) is really one of the only ones where you can have world-class competitors at the ages of 12-16, and that trend is getting more popular as speedcubing evolves. It almost feels as if speedcubing has become the new cupstacking for when cupstackers outgrow cupstacking. We have world record holders as young as 12, which is awesome really.
I would be interested to see stats like who is the oldest official sub-10 cuber, or even sub-9, and see how dramatic the age drop is when you see who the oldest sub-15 or sub-20 cuber is. For example, if I get a sub-9 avg this weekend at a competition, I think I would be the oldest fastest cuber (sub-9, 26.17 years old). It'd just be interesting to see and know I feel. Who cares if it even gets recognized officially. It would be cool to say I'm the fastest cuber in my age group (25-39), or someone holds the master record. Other sports have "Age-Groupers" and as speedcubing evolves, I think it might make sense to have a Pro category as distinct from age group competitors. Imagine having a Pro Card for cubing lol.
EDIT: It would also be interesting to see how age trends have developed over the years since 2003.