I practice "unread zero". I leave emails in my inbox in case I need them later. The search function works well. If they are not marked "unread", I don't pay attention to them thus my brain does not see it as clutter.
I think it's because of search. I know I can find something when I need it because everything is in one place, on one server, regularly backed up to 3 different locations.
NB My Inbox has 16010 items in it ;-)