I always wondered about this, so a little bit ago I decided to do some math on this.

So, Thor says he is 4'000 years old in Infinity War. Now, he could be rounding up or down, I have no clue but I'll just take it as 4'000 straight up. But, I decided to work backwards to when Thor first appeared in the MCU in Thor (2011), which is 7 years prior, so 3'993. Hemsworth was 26 when filming the movie in 2010, but for this one I'll just round up to 2, which he would be later in the year.

Anyways, so Thor should be physically 27 at this point and maybe most the MCU. Obviously Chris has aged 15 years in real life since then, but can't do anything about that. Anyways, so, I took 3'993 ÷ 27, which equalled 148. So it seems it could take him 148 years to age physically a year. This is what I think, but has anyone used different methods instead? Like do you go backwards from 4'000 exactly, and do you use Chris's age when he filmed Infinity War. I'm interested to hear thoughts.
Figuring out how long it takes Thor to age