Such a good idea. Now I’m going to get asked why I’m hoarding used containers!I have friends save containers for me. No way I could eat 70 containers of cottage cheese or yogurt! I've gotten about 3 years out of them, before they get brittle and start breaking.
On transplant day, I dig the hole, then carefully take off the lid. Set the pot/plant into the hole, and carefully slide the pot up over the plant. The taper of the container makes it easy to clear the dirt and slide the pot off.