I had braces for a long time, and the dentists gave me the same deal. My bottom row has a retainer glued onto my teeth, which I hardly notice anymore. They gave me a retainer for my top teeth, but I stepped on it years ago. Since then, my teeth haven't moved. The only one that has has moved a few fractions over, and isn't noticeable at all, I can feel it with my tongue that it's different, but that's about it. My teeth were incredibly crooked when I was younger, too. You can start to tell if your teeth begin moving, I think it might be different for everyone, so I guess if you start feeling your teeth shift, you should talk to your orthodontist.