The best thing for overwintering plants in pots is to get them dormant and keep them dormant. What kind of plants and pots are involved?

tj

I agree.
I mulch my Japanese Maples with leaves or bury the pot in a trench or raised bed not being used for winter garden.
You could do both being in zone 6.
Dig trench bury pot to the rim of the pot & mulch with leaves, not compost, compost could cause the trunks to root.
If you are going to do this every year in a place not used in the Summer. Then bury an empty pot to sit the planted pot in. The empty pot must be the same size as the potted plant pot. That way you will not have to dig a trench every year.