I had orthodontic treatment in middle school. It wasn't severe, but I had a protruding lower jaw, and I think I wore braces for about 2 years. At the time, I remember it was around 2.5 or 3 million won for metal braces..? It was in a regional area.
But thinking about it now, they gave me a retainer back then.. Since I was young, I thought, "Why do I have to keep wearing this when my braces are already off?" so I think I wore it for a few months and then stopped.. Time passed as I just avoided things like resting my chin on my hand, and I became an adult. Even now, I still have a normal jaw position. but.. when I bite down, it is slightly misaligned.. This might be because of my eating habits, so I just accept it and live with it.
Conclusion: Even if you don't wear a retainer, it doesn't always relapse? (depends on the person/case by case) No issues for 16 years