25/26 is just the age when male tennis players reach their peak. (Not Nadal obviously because of injury.)
Depending on the age when they appeared on the Big Scene.
Rafa was already close to being a top player at barely aged 18 - the age at which he won his first RG GS title. You just cannot expect him to go on like he did as a player who didn't emerge at the top at before hitting 23...
Rafa, despite his relatively young age, is already a veteran. It's not the age, it's the mileage that counts most of all - in 95% of cases.
I just hope he'll be able to keep it up at the top echelons of the game for the next couple of years.