We had a recent event where a ham was sitting on or otherwise keying his mic unintentionally. Unfortunately, the ham's rig was tuned to the 147.06 repeater! This caused the repeater to become unusable, of course. The repeater itself will timeout if a station transmits for longer than 3 minutes.
Unfortunately for the rest of us, the unknown ham was still transmitting after the repeater reset. This went through about three cycles before the unknown ham's unidentified transmission finally ended.
Fortunately for the rest of us, this did not happen late in the afternoon of May 10.
The moral of this story is this: dig out the manual for your radio, whether hand-held, mobile, or fixed, find the section on the time-out timer, and set it. Three minutes (180 seconds) is a reasonable length of time and matches up well with our repeater's setting.