The biggest fear is losing power for more than a day or two in real cold weather. Yes, you could have all your water lines drained and/or filled with a safe antifreeze and the traps filled with it also (to keep sewer gas from building up in the house) and you would have to make sure you had nothing in the house that could freeze, but when you "restart" the system you might have leaks from seals that dried up.

It would be very helpful to hear from anyone that either drained their system completely or had antifreeze put it.