I've seen UPS batteries fail in as short as a couple month's. Get a electrical storm and boom, all gone... WD, I'm guessing you didn't realize the battery was not holding a charge anymore as you wouldn't notice unless the equipment connected to it was on and you lost power and watched the computer power down. Some UPS's will start blinking or chirping at you at the end of service but a lot of them won't tell you at all.
You should see how quick a UPS dies in a place like a Radio Station. Lightening strike, 80 foot tower big antenna and boom all dead...
Sounds like they need some SOLA line conditioners.