The guy just turned 40. That is a pretty high number for an athlete, especially a football player. He is playing against some guys that are literally half his age. But that has not stopped him yet, and it wont for a while.
Tom Brady is also the best game manager. He always has been. In fact, people seem to forget that is really what he was up until his first Super Bowl.
With the combination of his health (God-forbid anything drastic happens) and his game management ability, Tom Brady can continue to play at a fairly valuable level for plenty of time.
Think about it.. He probably has maybe 1-2 years of being elite left. Then on top of that, he'll have a couple years of being a good player and then a year or so at a pretty good player. We're already up to 5 years and counting.
If things go according to what I am sure is his plan, there is no need worry about his body breaking down. Now, a freak accident or injury is different. Far different. You cannot prevent those or even predict them. But in terms of overall health, Brady is good to go.
He has never had the fastest feet, the strongest arm, or the physicality to bang around. Brady is a game manager, a winner, and a legend. He is going to be able to win football games for plenty of years to come.