Organ transplants are for life, not just 36 months.
If you want your patient to keep the organ transplant after going to all the trouble of finding the organ and putting it in, the patient must take their immunosuppressants. This concept should not be hard to grasp.
If you want your patient to take their immunosuppressants, getting the medication must be easy and reliable. You could:
a) lean on the drug companies to make the drug available at cost
b) ensure that everyone who has an organ transplant has enough income to easily afford them
c) require that everyone who has a transplant be on private insurance and require private insurance to cover the medication without question, exception, or time limit
d) pass The Comprehensive Immunosuppressive Drug Coverage for Kidney Transplant Patients Act of 2009.