This problem is usually preceded by slow heat up time.
Other things you can check:
Part Fan: is it possible the part fan is set too high, cooling the hotend?
You may get a bit more life by doing a PID auto tune : M303 E0 S200 C8 (takes about 10mins to complete).
I usually run that command with the Part cooling fans on. If the heater error occurs during that command, again, just replace the heater cartridge.