GO, MAX & MEGA kits always benefit from a heating mat, as a kickstarter (when below 25 celsius). An OHM kit never needs it.
Never put the growkit directly on the heating mat. Always put something in between, such as a folded towel. If the growkit gets too much direct heat from the heating mat the mycelium will loose all its moist.
Use the Heating Mat only the first 2 days, right after setting up the kit. The Growkit will be kickstarted, and does not need extra heating anymore. The brick could become too dry, and not produce any shrooms anymore.
It's recommended to get a mycelium Thermometer in combination with the heating mat.