If you don't heat your home for a while, and it's cold enough, the pipes can freeze, break, and flood your home. It's happened to more than a couple of people I know and they're in the UK - so it doesn't need to get very cold for it to happen.
This, plus I don't want to return to a completely cold house that takes about three days to heat up to 20 degrees Celsius again. The building is built of bricks, it has a certain thermal mass and the floor heating isn't very powerful. Letting the inner temperature to drop close to zero would mean a very uncomfortable period after return.
I was never absent for more than 5 days anyway, so...
