Though Tyson doesn’t care about his birthday or his current age, he is aware that with every year that passes, Tyson inches closer to redundancy within the web; and looking even more like his father. Minus thirty years or so, Tyson is already the spitting images of his father and those thirty years are gradually trickling down.
Tyson knows how to make himself useful and his role in the web isn’t dependant on his physicality, but the less able he becomes, the less Tyson can do for the Moriarty Mirrors. The less useful he becomes to them and the more likely that he becomes boring.
Tyson would walk himself out back to be put down before he allowed himself to become a liability to the Moriarty Mirrors safety, or to the safety of anyone else he cared about. He can’t reliably judge how interesting he might be to his Darling owner’s, however.
Before Tyson needed to worry about that, his age was a non-issue to Tyson. He didn’t care about his birthday, but Tyson didn’t spare any thought to how old he might become. He expected to die in service to the army long before he reached retirement age.