I had some replaced. A few years ago I told the dentist I was unhappy to have them and wanted the other kind in the future. She poked at them, said they were loose, would have to be replaced and did so. I think it's considered a dental emergency if they're loose, because eventually the tooth will ache like a new cavity.
The remaining two are too large to be replaced. I decided to have the teeth extracted even though one is near the front. Partial dentures are covered too for me, but not sure if I want plastic and possibly a steel hook in my mouth.