http://zqktlw5bf6oycxq6qod452xnvdfcqhfwliz54bkul736g6b454jrk2ad.onion/wiki/index.php?title=Physical_Interaction
Ideally, the physical location that you ultimately have to go to to pick up your mail should change every 12 months. If your budget and need for anonymity was high enough, one way to increase the length of this window is to attempt an SSH Hopping -like technique by chaining virtual office forwarding systems together to attempt to obfuscate your location by crossing many international boundaries.