It's good to know that you got at least three good years out of yours! Can file Key Fobs in the No Worries folder for now!
It really depends on a few factors, but in-particular, two stand-out:
(1) The Q/C on the 2032 coin battery - not all are created equal, and even then, every once in a while, a "bad one" will still pop up out of nowhere (REF:
https://www.ascentforums.com/threads/key-fob-battery-life.20499/). If you have a battery tester, it's worth it, in my book, to give it a quick look-see before popping it in the fob (even though one can still gain ingress -although I'd encourage everyone to check their emergency key, NOW, to insure that it works properly (REF:
https://www.ascentforums.com/threads/manual-key-will-not-mechanically-unlock-door.20174/#post-230721) - and start the vehicle with a "dead" fob (see video [not mine] linked below] it's, well, still an upsetting experience for those who aren't expecting it and who may not know how to do it). If you don't have a battery tester, Energizer or Duracell are both easily had (the trick to getting Panasonics via "mail order" is that you'll want the genuine ones), and of reasonable quality and consistency.
(2) Are you one of those OCD or impatient folks who love to hit their lock/unlock buttons repeatedly, as you approach or leave the vehicle? I am, and yeah, that causes the battery to discharge faster. 😅 Solution? Use the touch-enabled locking and proximity unlocking feature - and if you have one of those OCD moments after you step away? Log in via MySubaru/Starlink.
(3) There's more than anecdotal evidence -from virtually all brands- that suggests that having a smartfob too close to the vehicle will cause the vehicle's battery to drain, but that the reverse can also happen: that the fob's battery also seems to discharge much faster. Either keep your fob far enough away from the vehicle to allow the vehicle to go to "sleep," or, alternatively, purchase a Faraday-cage type "valet" to store your fob when you get home.
Hope this helps!!!
