Knowing what others have theirs on doesn't help. Not one bit. There are too many variables!
Placement of the thermostat is one. A heating system works to the thermostat - if the thermostat is nearish to a radiator the heating will turn off sooner than if the thermostat is in a hallway with a draft. It will turn off before the sitting room has reached temp if the thermostat is near the rad in the hall way.
I have a remote thermostat, if I put it in the sitting room it gets to temp quite slowly (big open room) but if I take it into the study with me it gets to temp quite quickly (much smaller room). The temp is set the same.
Does that make sense?