I winter mine over on a northwest windowsill, in their original pots. I make sure they don't totally dry out, but I don't feed them either. It's cold there, too, but not freezing.

The plants grow a little and produce some flowers on occasion. But come spring, when I put them outside (gradually) I cut the stems back and feed them diluted Miracle Grow, and they take off like gangbusters. I've successfully kept geranium, fuchsia and agastache going for years this way.

i pull all mine up in the fall, let them dry a couple of days, shake most of the dirt off, put them in paper grocery bags, store them in the basement, bring them up in march and pot them up in miraclegrow potting soil. in may they aren't as advanced as the plants at the nurseries, but if you saw them today ...