Father TIME catches everybody. It is not a question of if, but rather a question of when. Tom Brady is no different, even if he is The Greatest quarterback the NFL has ever seen. Nobody knows for sure, and for all we know Brady doesn't know either. He may be taking a year-to-year approach.
With the amount of care Brady puts into his body, I don't see how he could wear down.
Although, injuries are unpredictable and can happen in an instant.
The Decision
There are a few factors here that will have an impact on how much longer Brady plays.
One is how well the team does. I believe that if the team wins another Super Bowl, Brady could hang up his jersey as soon as his contract expires after the 2019 season.
Another is what the team wants to do. The past few years have indicated that the Patriots are going to do everything in their power to keep Jimmy Garoppolo, which means the Patriots believe he is the guy for the future. However, if Brady is still playing at an elite level by the time his contract is up, this creates an interesting scenario.
At that point in time, Brady will be 43. The Patriots will have to ask themselves do we want a few more years with the greatest ever or are we ready to move on and finally give Jimmy a chance?
The tough choice
Personally I don't see how the Patriots would resign Brady, even if he wanted an extension. Garoppolo has showed enough that he may be something special in this league, and if we keep Brady for even longer we most definitely lose Garoppolo via free agency, and we will never know how great he could've been with this team. Is it really worth sacrificing what you think is the future for one or maybe two more years of glory? What happens if it doesn't work out, then your left with no quarterback that you believe in for the future.
I think once Brady's contract is up, they will move on from him. I don't believe Brady would be interested in moving to a new team and getting used to a new system and area. I think at that point he would call it quits. But I am not Tom Brady, and maybe he truly wants to play until his body won't allow him to anymore, even if it means playing for a team that isn't the Patriots.
Brady knows his time is almost up, and he has been noticeably trying to build up his brand more aggressively in the past year. He has been in way more commercial ads, writing his own book, and even made an Instagram to help branch himself out because he sees the light at the end of the tunnel and that there is life after football.
The bottom line is that Patriots fans need to enjoy it while it lasts because even the best-ever have a timer on them.