Yeah…I spent a lot of time thinking about that phenomenon when my grandfather was 95+ a couple of years ago. Each year passes noticeably faster than the previous. I think it's down to plain old mathematics. A year seems like forever when you're four years old, because it is between 25% and 33% of the total time you've lived, so in the context of your accumulated experience, it is practically forever. The same 12-month period speeds past when you're 31 years old, because it is just ~3.2% of the total time you've lived. And by the time you're 60, a year is 1.6% of the total time you've lived, making it equivalent to only three weeks as a 4-year-old, in the context of your life's accumulated experience. My grandfather lived to be over 96 years old. In his last year, a one-year period rounded down to 1% of the time he'd been alive, which is perceptually equivalent to just under thirteen days as a 4-year-old. I know all that intellectually, but time's acceleration still astounds me every time I notice it.
(And that is a long, flowery way of saying "Time flies when you're having fun" or "A watched pot never boils" or "Time flies like an arrow; fruit flies like a banana").
