engteach thats what they are meant to be left on all day and night if wished, we call them slow cookers, the modern ones have several different settings, so if you really afraid of leaving it on,put it on the lowest settings,i have had mine on since yesterday evening, and wont switch off, until i have supper tonight!!!
I`ve known people who are scared stiff to use a pressure cooker in case it explodes, despite the fact they have two valves to release excess pressure. As puddicat states, slow cookers are designed from scratch to be left on for very long periods. You probably have electrical devices around the house that are on all the time, alarm clocks, timers etc., or others on standby. It`s gas leaks, ancient wiring,chip pan fires & human error that cause virtually all the household problems. We`ve had our crockpot & pressure cooker for nearly 30 years with no problems.