Since we put the topper on, we have not used the mattress heater.
It keeps us toasty even when it is cold outside due to the extra insulation it provides. We do have an aftermarket AC wall heater to warm the master bedroom when we have guests and the doors to the bathroom and hallway are closed (no registers in the BR over the 5th wheel hitch).
Envi High-Efficiency Whole Room Electric Panel Heater - White (Model # HH1000) - eheat.com
Works great. Pricey, but only 450 watts at full power. Mounts flat to the wall and is cool to the touch on both flat sides.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW