And to add onto this; Mayweather kept boxing as long as he did because he was above every competitor - not because he was peaking later or some other arbitrary reason.
Mayweather could keep boxing at the level he did for as long he is, because like Bernard Hopkins, he treated his body like a temple. He doesn't drink, doesn't do any drugs, has the best nutritional advice and recovery programmes available to him.
You can have all the talent in the world, but your body ages like everyone else. Treating his body well, and advances in nutrition and sports science is what helped preserve Mayweather and Hopkins bodies, speed and reflexes for long than average.