Being behind people like that is why I ship from home!
Seriously, all of you who constantly buy and sell, invest $15 in a digital postal scale, print your postage right from eBay (or Paypal via USPS.com for non eBay items), and give 'em to the mailman.
Or, just prepay the shipping and just drop them off, in a mailbox if they fit or at the post office.
It's 2016, I see no compelling reason to actually go to a post office!!