depends on outdoor temp and the thickness or thinness of your blood. everyone is different, dont ever tell the homeowner they should set there stat at a certain temp or when they get a high bill they will want you to pay it, CYA EVERYDAY
I typically keep my place around 72-74 in the winter. Once spring and fall hit I'm happy with a little bit cooler temps (because I'm not trying to thaw out from working all day in the cold). In the summer my house is around 80-90... but I don't have A/C yet lol.