If the joint disc is recaptured successfully using splint TMJ treatment, does the issue ever become cured? Is there any point where an oral appliance doesn't need to be worn anymore and the joint is fully healed/normal?

In a perfect world. The therapy can help to heal and stabilize the joint. However, we often have habits that can stress the joint and supporting structures, like clenching, These need to be stopped or preventive measures instituted. Consult your dentist.
Cure perhaps. Most TMJ problems are chronic. The disc is not truly "recaptured" Tissue adapt to new position. Many times oral splint can be discontinued.
TMJ Splint. your treating dentist knows your condition well and is best able to advise you on this question. It will depend on the amount of damage that was done, the amount of healing, your habits, lifestyle,general health. Do not stop using the splint without advise from your dentist. You would risk a relapse if you stop using the splint.
TMJ Treatment Sucess. Jerry; Most definitely if the joint disc space is captured successfully the appliance would not be necessary. However, in some instances extensive occlusal reconstruction is required and the patient doesn't wish to receive further dentistry. Secondly, stress aggravates the joint and frequently the patient requires using the appliance for a few days until their symptoms subside.
Not possible. It is not possible to achieve a normal disc-condyle relationship or "recapture" the disc for a long time using TMJ splints or surgery.
Depends. upon the amount of damage the joint has suffered due to malocclusion (the most common cause of TM joint disease) If the damage is minimal it can heal! Hope this helps! Dr Z.