I do agree that if the storage time is too long a trash can would be used as in place of a teleport spell. So, as another poster said, make it short enough to not be useful for that. 5 minutes would be reasonable and hardly usable for more than minor movements. And I could see somebody putting their building into the trash to make room to move things around, then forgetting they had only 5 minutes though. So the trash can has a countdown before the "garbage" is collected. That would teach them the purpose of the trash can, of course.
AJ