I'm honestly not sure. But I know that for most systems (central, or whatever) they generally tell you keeping a constant temperature (whether cool or warm) is easier on your systems than trying to cool it off once it gets too warm, or trying to warm it up after it gets too cool!
We do keep our heat a LITTLE lower in the day because we're up doing stuff and it can be too much when you're dressed and up "juneing around" as my mother would say! But at night, we only raise it a degree or two and that seems to be just fine. Plus we have a matress warmer for the bed and two labradors keep us toasty (and crowded) too!
