It is wonderful when you can meet them. A co-worker's nephew was in Iraq and we would send him huge boxes of stuff, plenty so he could share. Movies, books, snacks, cigars, along with items from a list of "what sort of stuff they need". That was really fun to do. After a few years he came to visit his Aunt and we got to meet him in person. It was excellent.
My wife and I were supporting a soldier and his squad. We'd get an occasional letter. Then we got a letter, KIA. I never met the kid, but I cried as if he were my own.