Re: To be fair...
A occupied house always retains heat to a degree, left unattended for even a few days will see it cool.
Having worked away from home for a number of years, leaving on Friday afternoon then coming back to my flat on a winter Sunday night was a much much colder experience than the rest of the week (Returning after Christmas\New Year especially) was not fun.
I got around it by having a oil filled radiator on a timer so it would keep a modicum of heat for Saturday & really start heating up the place in late Sunday afternoon.