You're doing fine Monkeypaws.
You don't need multiples, it's just nice to have some should you lose a disc, especially if you're playing a tourney. The putters some in handy, but you already have 2 Aviars, so that's fine. It's just more effective to practice putting and not have to walk to the basket so many times to fetch your discs. You can get more reps if you have 4-5 of the same putter.
Many experienced players use multiples so that they can throw a few molds, but cover many shots with those select molds. Watch the pros "in the bag" videos. Most of them carry more than one of each disc, in varying degrees of wear. (This is what Kaiser Flipping was alluding to)
Edit: Looks like a couple posters said basically the same thing while I was typing my post.