"I used to let my PO Box fill up with crap and then chuck it! I got so much darn junk mail, and didn't use it much so it sat for months."

I believe a PO box -- which is paid for -- is different than a package sent to General Delivery. Yes, I just checked, and a package sent to GD will only be held for 30 days.
http://www.usps.com/receive/choicesfordelivery/receivemailinotherplaces.htm