We've used Express Scripts for years. On a recent trip that lasted longer than we planned, we saw a script coming due for my wife. Using their website, we set up a temporary address for that script only. Worked like a champ, then it all reverted to our normal home address. The KEY is staying proactive, and work those prescriptions before they ship them!
BTW, we are NOT full-timer's, and live 2 miles from an AFB with a pharmacy. But neither one of us wants to wait in that line! Let it come to our mailbox, on time, and generics are free!