I thought I would share a tip. I use Avery 6461 address labels for my letters to my grandson. They are actually removable multipurpose labels. They stay on the envelopes AND he can peel the label off and use it for his return address. That saves him a lot of time that he could use for writing letters. If you have ever seen a military address you will know what a great tip this is!
I don't use one for my return address though because I'm not sure it would always stay on for the return trip. But after it leaves the base it doesn't really matter if his return address stays on or not (but it has always arrived with the label on.) We can't send him anything but he can recycle!