Ours stays at 70 all day. I get cold easily, so 68 is just too low.. Plus we have a second story that we only use at night.
I definitely think 75 is too high, no matter what the temp is in the house or outside..
Oh, and the person that made the comment about 75 in winter and 65 during summer.. I know what you mean. Typically we keep 70 all winter cus the kids and I are actually home. In the summer, I wait until the last minute to turn on the AC. I freeze during the summer because my husband likes it cold..And he burns up in the winter because I like it hot.