Heating elements can fail. These are relatively easy and economical to replace. The heating element is not necessarily the culprit if your tumble dryer does not get hot, however. There are thermal overload cutouts fitted to many machines. If they fail, the current will not be passed to the heating element. Replacement is again, fairly straightforward.
Tumble dryers will often have thermostats fitted. A heater control one, and an exhaust thermostat. The first keeps the temperature correct. The second, as its name suggests, monitors the temperature of the exhaust (in case the airflow in the machine is impeded) Once again, replacement is not too much of a problem.