Here [0] is the datasheet for the batteries used. 25 year shelf life is spec'd.
I have personally run these cells buried underground, and gotten 4.5 years out of 4 of them, though my application is just for fun and likely not as power conservative as an AirTag.
So I attend this local annual event that has a time capsule. Each year, we bury one and dig up the one from 5 years ago. This has gone on for several decades, and people are always thinking of interesting things to put in there.
I made a little electronics project that is somewhere between "what happens inside a time capsule while it's buried?" and "what if you could wind a watch once and have it still be ticking in 5 years?"
I have personally run these cells buried underground, and gotten 4.5 years out of 4 of them, though my application is just for fun and likely not as power conservative as an AirTag.
[0] https://data.energizer.com/pdfs/l91.pdf