Forget the winter, we are still using the heat almost all the time and it's late in May..
Today, it got warm out. At long last. But, the temp just dropped pretty quickly to 57F.
I just ran around shutting all the doors and windows.
At least we had a few hours of fresh air.
We keep the house at 20 to 21 C.. (68 to 69.8 F).
Since we are retired now, there's almost no time of the day, when the house is unoccupied.
If we both go out, we leave it at 19 or 20, if we plan to return within a few hours.
If it's mild out and looking like it might warm up, it goes off when we leave.