I'm in zone 6 and usually wait until frost, then dig them and store them in peat moss in the garage. I have dug them early (to send them for a trade) and they seem to do fine either way. I've also just brought them in and planted them indoors under lights in the basement and kept them going the entire year round, then put them back outside in the same pot for the summer. Still going for two years now. I think they are pretty hard to kill unless you freeze them and let them turn to mush!

Tiff,
I am in about the same zone as you are, and I never dig mine out. Just remove the leaves turned to mush after the frost. They come back year after year, and multiply like crazy.
Natalie