there are always some that'll hold into March.

Cannot say for MI - but here - they are the minority,
I had a dozen fresh sheds before 1/1/2011 this year. Most were gone by 1/31.

As the snow melts away - I add a few more.

In my area - we got about 200" of snow this year. I'm finding my sheds in thermal cover - where they beasically spent January, right now.

Good luck