There are only two things I leave on when away from my boat, one is the Fridge and the second is the battery charger for bilge pump purposes.
Sometimes I have been on the other side of the world from my boat plugged in and alot of other times I have been on the other side of the country.
The key is to have a good liveaboard near by who doesnt mind keeping an eye on your vessel when they walk by, give them your phone number and keep your insurance up to date.
Just last week a liveaboard here noticed a 35' leaning over in one of the slips and the bilge going, he called the marina staff who hauled the boat and found a leak with 8" of water in the boat.
Thats why its important to be nice to your dock neighbors..