I had braces around 5 years ago & wore my retainers like they said until I took a trip in 2017 where I stopped. When I put them back on they didn't fit great but they still fit enough that I didn’t feel like they were a problem. I then noticed my retainers had cracked. So I went to get new ones and they made them thicker so I can't crack them. They are EXTREMELY uncomfortable for me to wear now. There's a gap between the roof of my mouth and the plastic & the plastic cuts into my tongue on the bottom