While my situation may be different from reefried i also don't need to use a heater on my 75g. (Well i have one set up in case temp drops to much but it never goes on) My house temp is a very stable 73 degrees in winter, and add in the heat equipment gives off the tank will be about 75-76 degrees. I leave my canopy open when the lights (T5 X 4) are on which allows most extra heat to escape. my tank will hover between 75-77 in the winter time. So for the right conditions a heater can be optional, but i still have one as a safety net incase for whatever reason the tank dips below 73.
Still great list to follow even though there are always exceptions to the rules