Advice in how to properly maintain my UPS

First of all, I hope this is the right place to ask. I have looked around and this seems to be the correct place inside SE. I do not own a server but I use a really old APC Smart-UPS SU1000INET for my PC. But hey, it works like a charm. I bought it last year for like 40€ with fairly new batteries. (I think they had a couple of months of life back then) Now, I want to maintain it properly and I wanted to ask for advice here. I check it's status etc with Powerchute Business Edition (since it's the only version of Powershute that detects this ancient piece of technology) and everything seems righ

Question by S. Dre on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.