Hello and thank you for your question.
If you are seizure free for 23 years than you should see a neurologist who can clinically evaluate and help you to wean off the medication. You can wean tegretol off slowly and stop the medication if you did not have seizures in 23 years. However your doctor has your medical history and it would be his judgement to stop or continue or lower the dosage.
Long term side effects of tegretol is that it can affect liver, cause low blood count and can cause skin problems.
Tegretol has also been linked with bone marrow suppression in some patients.
Regular blood test and bone mass testing can help to evaluate if you are having such side effects or not.
Please get back to me if you have any further questions. Thank you.