minimum stores not for winter

During the season,I like to see 20% of the frames with honey or a bit more if nectar.
Late winter, early spring, and during our midsummer dearth are critical times to inspect for low stores and possible emergency feeding.
In my area(northern CT),pollen is available pretty much continually in the warm weather and frames often become pollen bound in the fall.

I would look for a few (2-5) frames of stores. With 4-5 boxes for the brood nest 30% stores would be a lot. It also depends on the season. Less stores when the flow is starting is less of a concern than during a dearth.