Sort of like Zeno's Paradox? You never get old because when you're sixty, people say, oh sixty's not that old, seventy is old and when you're seventy, people say seventy is the new fifty and when you're eighty people say eighty's nothing, people are living past a hundred all the time these days...? Something like that?
Edit: but in this case, collectively, what everyone understands to be old changes and say it was 70-80 but now it's 100-150.
Or even better time itself becomes nebulous as you get older. Like the task that use to take 60 mins takes 1 minute because what everyone understands to be 1 minute to be changes.