The default thresholds catch a UPS that's already failed. Here's how to tune them to catch one that's degrading.
The default alert fires when estimated runtime drops below 5 minutes, which is often too late to act. Add a warning-level threshold around 15–20 minutes so there's time to gracefully shut down dependent load before power actually runs out.
A UPS running at 90%+ load has little headroom if a redundant unit fails; set a load threshold independent of battery status so you catch capacity problems before an actual outage forces the issue.
Most UPS MIBs report last self-test result and battery replacement indicators. Alerting on these catches a battery that needs replacing well before a real outage reveals it can't hold a charge.