steve26 said:
I know very little about cycling but am curious what age a cyclist in general is considered in his prime?
For instance in tennis you are very old at 30....
You know, tennis is pretty much the same everywhere - you have different surfaces and play in different temperatures, but a good tennis player is good any where and any time.
Golf - kind of the same thing, some courses may favor better putters and others longer hitters, but a good golfer can win on any course.
Bike races can be very different - climbing, time trialing, windy courses, cobbled coursed, all the different kind of track racing. A great climber could never win a short windy race, and a great sprinter will never win Alpe d'Huez.
Younger riders recover faster, older riders know how to suffer more, generalizations beyond that are hard to make. There have been young superstars who faded away, and old guys who came from obscurity to win in their later years. The best riders adapt to accomodate their body as it ages.
By not answering your question, I'm saying that the answer you're looking for doesn't exist.