If the plants are well grown and hardy, I leave them outside. We have a reliable snow cover, but very early spring can be critical. I tend to worry if we have a January thaw followed by rain.
If the plants were expensive, are immature, hard to replace, etc., I overwinter them in an unheated house with a frost blanket over the plants and opaque plastic covering the house to keep the light out.
We don't have great luck overwintering plants grown in soilless mix.
Hope this helps.

I leave mine outside and cover them with a thick covering of straw. I have at least a 90% success rate even when temperatures stay in single digits for a lengthy time. I uncover them in the spring and repot them to bigger pots.

Thanks --- I have ended up putting them in my sales area which is 30x96 cleaned them up and let them freeze and put frost blankets over them . They still look good. I have a lot of odds and ends that I haven't tried wintering before should interesting . It sad that I have that many perennials left over . Hopefully this year will be better .Do you bump your pots 1 size when you repot ?? Thanks -------+
Upnortdareh

Bait for crits under those blankets, or you might find a lot of plants gone.