Under normal circumstances, my room temp runs between 70F-72F. Since the tank's pumps & lights add about 7-8F degrees, the heater is almost never needed.
The exceptions would be if the heating system broke down. Since I have a heat pump with electric back up, failure is a small possibility. But during total failure where the house reached say 40F in winter, I doubt 150 watts of heater would help much in such a scenario, but I have another 150w on the shelf.
I can correct any environmental issue if I'm not traveling or on vacation. Undetected failure of heating or cooling at the wrong time is my primary vulnerability.