I can't see Rodgers performing at a high level much past 40. He is more like Ben Roethlisberger then Tom Brady. Big Ben has looked more like a pudgy middle age adult rather than an elite athlete for a few years. For Rodgers, it's more his face and bags under his eyes making him look middle age indicating to me that he doesn't get enough sleep and take care of himself nearly at the same level as Brady.
I believe that to play at an elite level into the 40s, one must be disciplined in taking care of your body in everything. Sleep, food, hydration, stretching, strength training, rest, vitamins, sliding, not going for a fumble and being piled on (last NO game), etc.