Winter - Away - Turn Off Heat - Drain Pipes

[Descant]

Originally Posted by camp guy

... "Draining the pipes AND keeping the heat on at a low setting will probably solve both issues. The cost off the extra fuel to keep a house at a low temperature during the winter is significantly less than the cost of the repairs necessary when you try to DIY and cut corners..."

I'm mystified here.
1. If I drain the pipes (radiators, baseboards, whatever) how will I keep the heat on at 50 F?
2. If I don't drain, and keep the heat at 50F I'd guess I could easily use 300-400 gallons of oil at say $6.gallon. Let's be generous and say 150 gallons, I can get the ceiling patched/painted for les than $200.
3. If I keep the heat on, I probably have to pay somebody, or get a neighbor, to watch things to make sure the heat doesn't fail (run out of fuel?) And, what if electricity is off for several days? The pipes can freeze anyway.