My average tumbler time is 2-3 hr.
It is never a good idea to let an electrical appliance run without supervision. It is your house and you make the call.
do you ever turn the dryer on before you go out? better make sure you shut off your furnace and fridge and deep freeze, im sure you know how hot those refidgerant compressors get
i have no probs leavin a tumbler running when not at home