For whatever it's worth I have a personal counter-story to airtag usefulness. Not to get into the debate of indoor vs outdoor cats, we had a cat a few years ago that liked to roam around outside and one time it got spooked and disappeared for two weeks. It came back all skinny and hurt and after that we bought an air tag collar for peace of mind. The airtag worked just fine for a few months until the cat disappeared again. That very day the airtag stopped working so when we actually need it, the signal was permanently lost. We never found out why. I could imagine perhaps a car hit it or a coyote ate it, but there's certainly edge cases where an airtag would fail immediately. Battery life is highly unlikely to be the culprit in my opinion as it was fairly new, working recently before that day and the timing was too perfect.