How long would someone be on immunosuppression meds after kidney transplant?

For life: A successful transplant can have the dose of drugs reduced over time, perhaps some of them discontinued, but even the best matched organs will need continued immunosupression. Identical twin transplants, which are rare may be an exception.

Forever: If you stop immunosuppression the kidney will reject. Therefore you will need to stay on medication indefinitely.

Life long: Some immmunospression is needed as long as the graft is working.