Our six year old Kenmore Elite Dryer cuts off when drying a load of clothes before the timed cycle ends (just a 10 minute load). The dryer is hot inside and yet it just shuts off. The venting is clear. I am not sure if it could be the heating element thermal cut off, a thermistor, thermal fuse on the exhaust duct, dryness control board or the high limit thermostat? I would like some advice on this problem. Thank you.