I say he will give us three good years, then he'll be gone after that regardless of his physical conditioning. Teams just like to invest in youth as opposed to in age. At 35, he'll be at that age where teams are looking to release him and add youth to the squad.
TO has an excellent work-out regiment, one that rivals Walter Payton's and Jerry Rice's. That benefits him well in terms of longevity.
Second, he's not really a burner. He's strong, a good route runner and is a break-away threat on determination and hard work. I think with those traits he'll last longer than a receiver who simply relies on speed.
Third, he won't get the ball as much as he did in a WCO. The balance will probably add a few years to his career.