Some tooth splints are permanent while other tooth splints are installed in your teeth temporary.
If the tooth splint is temporary then the temporary tooth splint will usually last for up to 8 weeks and then need replaced or adjusted.
If the tooth splint is permanent then the tooth splint should last 10 years or longer as long as you have regular dental checkups.
The dentist may need to work on the tooth splint to maintain it periodically but the tooth splint when installed correctly by a dentist should last quite a long time.
If you notice something wrong with the tooth splint then you should see a dentist as soon as possible about it.
But you should not need a new tooth splint for 5 to 10 years and sometimes longer.