Re: Boxers Prime years
Assuming you never retired and allowed your body to heal up. If you fight non stop at the highest level (title fights), by age 37-38 you are pretty much pass it.
Wladimir in another 2 years will actually be on a steep decline and should seriously consider retiring after 2013 to avoid another Brewster/Sanders/Purrity which will hurt his legacy.
There are some exceptions like Sergio and Hopkins. But generally speaking and especially for heavyweights 37-38, you are done.