I've overloaded these as well, I really didn't expect to use these UPS for anything else but the following...
1. Stay running for the occasional brownout.. Little flicker off and on.
2. approx. 5min of runtime during a blackout, then power off all servers if power isn't restored.
3. Filter AC power for Pure Sinewave (Hardware longevity)
4. Surge protection
It is a pain to work with them.. they are heavy and awkward because the are small with no handles... Pulling them out of a data rack is no easy task. So I did put this off for a few months. But today I was mentally prepared!
How many hours are they suppose to run if it is not 24/7? You can laugh at me if you want

Any brands you recommend that are more durable then the usual ones that cause problems?
The UPS we are referring to, APC Smart-UPS, Line Interactive, 1500VA, is approx.
0.03386881BTC. It is my go to UPS of choice.. on 1,000W it will yield a runtime of 6mins...
Now, if you wanted 24 hours @ 1,000W.... 1 x APC Symmetra LX 8kVA Scalable to 16kVA N+1, Tower 208/240V and 4 x APC SYMMETRA LX EXTENDED RUN TOWER W/9 SYBT5 , 208V,
2.32111771BTCYou need to take into consideration many factors when deciding how long you need your servers running in the unlikely event of a power outage.
Most people will think forever until the power comes back online. But in practice this isn't the case. What's the point of having your server running, when everything is offline.
If you do need your server online 24/7 it may be best to have it in a DC where there is backup generators.
APC has been my choice for many many years! I am lucky to have a client who imports their own line of Automotive/Marine/MotorCycle and SLA batteries here in Australia. So a replace battery is a third the price from APC.