Maybe not forever. But maybe. And maybe almost never. What?
How much you need to wear your orthodontic retainer really depends on your own individual biology. We can't tell for sure whose teeth will relapse when the braces are removed or Invisalign is done but there are some clues.
Wisdom teeth- You need to be extra careful about wearing retainers when your wisdom teeth are still developing. Have your dentist check your wisdom teeth. If they are impacted or there is no room for the wisdom teeth, there is a definite chance they can start crowding your other teeth if left.
How crowded were your teeth when you started braces or Invisalign? The more crowded to begin with, the more the teeth seem want to move back.
Did you have spaces to start? Spaces just love to reopen. So wear your retainer and pay attention to spaces. If spaces start opening, wear your retainer. If they get bigger and bigger, see your orthodontist.
In general, we recommend retainers be worn nightly for the first year. Then start cutting back to every other night. Are the teeth staying straight? You can go to every third night and so on. You can start tapering off your retainer. Are your teeth moving when you do not wear your retainer nightly? Then you may need to keep on nightly retainer wear. Check with your orthodontist if you are not sure or you have any quetsions.