Don Shula has the record with 328. Belichick has 302. And Reid has 270.

Let’s say Reid ends the year at 273. If he averages 11 wins with Mahomes going forward, he needs to coach 5 more years to tie the record.

He’s 66 years old, so depends how much longer he wants to do this. But Belichick is 72 so 5 years would just take him to the same age that Belichick quit at.