Man, you guys have your's set lower then we usually do. We usually have it set to 69 while we're at home, 70 during the cold winter months from December till February. On certain really cold days, we'll up it to 71. The only reason we'll up it to 71 sometimes, is because we spend a lot of time in our living room, and it's the farthest from our furnace not to mention the duct work going to the living room vents has like a bunch of bends in it in order to get there, so it's not a nice even flow. So normally the living room is the coldest place in the house. I just bought a small heater for the living room to see if that would warm up the area a little more so that we don't have to have the heat up for the whole house as much.
Normally I'd drop it to only 68 in the winter when we're not home...and at the moment, my wife is on mat leave for a year so I can't really turn it down. She also breast feeds at night so I can't turn it down past 69 at night either until my son is sleeping through the night. I may just move that heater into his room and tell her to turn it on when she has to get up to breast feed.
In any case, once that's all over, I'm going to try dropping it to 65 at night and when we're not home to see what kind of difference that makes.
