You're just using the UPS to do filtering and condition your power. If that's the case, you've got some pretty crappy power there, although the UPS idea is still a good thing. A bit heavy, but still good.
What I'd do is somewhat strange. Bear with me. In this example, I bought a used VHF antenna distro just last week. It was sold as-is via Ebay. I plugged it in and tested it for 18 hours. It's fine.
My idea for you is similar to what you're currently doing. Just whatever you think your longest show would be, triple it. Can't hurt.
In my case, my longest show has been an event over 3 days(next year over 4 days, we're expanding!). And my on time is 10AM to midnight, so I gotta be spot on. But antenna is easier than something like what you're dealing with since you've got more things to be concerned with.
And just a note for readers:
Filter your power. Your gear will thank you for it and it may resolve a good deal of problems.