My UPS battery lasted for about 8 years. Now, it won't hold a charge. I only found out when I had a power outage, which is exactly when I needed it.
What's an inexpensive maintenance routine for a UPS? For example, is there a brand that allows replacement of the battery only? If so, what's a good brand?
For UPSes in datacenters, we tell our customers to replace the batteries every two years. For home users, and if you have sufficient capacity, you might get away with three years betweeen replacements.
APC and Tripp Lite are the only brands I'd use professionally. At home, both are excellent and I'd also consider Belkin. Don't chain them together unless they are designed to do so -- APC in particular makes external battery packs for their UPSes.