We do it routinely, unattended. Our big coach has about 2300 watts of baseboard heat installed in various (5) locations including the basement. We run them unattended as well as when we sleep. We are full timers. If the outside temps drop below zero (celcius) the furnaces furnaces tend to kick on as the electric doesn't keep up. Again, routinely run unattended and sometimes for long periods. In your case you may need to put a solar panel on the roof to keep the battery up. If your trying to just keep it from freezing set the thermostats around 8 celcius and the battery will last a long time. Leave your cabinet doors open if there is plumbing in behind them.
Good luck.