retrolefty:
Why would overshoot/undershoot be a waste of energy. Is not all the heat energy generated directly going into the drying of the material? As long as you are not continuing to send heat into the material that is already 'dry enough' I don't see where the 'waste' is? Too much heat, time to 'dry enough' shortened, too little heat, time to 'dry enough' takes a little longer, no net change on total heating BTU consumed used to reach the it's 'dry enough' setpoint.
Allow me to disagree a bit. This is not a closed system. If you control the input into the dryer by monitoring the exhaust temperature, you can limit the excess heat being exhausted to atmosphere (in the case of dryers with flue pipes) or the house (in the case of condensing dryers). You also have to watch that exit temperature for the dryers typically used in the US to eliminate the chance of condensation inside the flue duct, even if you have a stainless duct that has been designed to drain. In a condensing dryer, you presumably want temperatures closer to condensation to help condense the latent heat out.
Additionally, there are benefits to longer drying cycles per the DOE or IEC test procedure. Since the test procedures prescribe a relatively dry room, you can benefit from the "dry" air being sucked through the appliance carrying off moisture without having to heat the air. Heating simply drives off the water faster.
Over-drying results in clothes that are no drier than they could be (i.e. "bone dry" is the limit) but lots of heat being used. In the US, that usually entails the excess heat being vented to atmosphere, in the EU, that eat is "recycled" into the home when using electric condensing dryers. In the wintertime, there is a marginal benefit, in the summertime, it just adds to the heat load of the house. Additionally, over-drying is bad for clothes.