How long to take Treatment?🤣

A few months ago an interesting incident happened during my consultation. A patient with Rheumatoid Arthritis who was sincere in continuing my quackery for nearly seven years asked me”Doctor. For how long I have to take treatment.”My immediate answer was “Life  long.”He asked me “Whose life long?”I replied “Since you are suffering from the disease it is your life long treatment.But there are three possibilities which can occur. If I die earlier which will be  the most probable occurrence because I am elder to you ,the treatment should be continued with some other Rheumatologist. If both of us die simultaneously then there is no problem since both of us are non existent. If the rare event of your death occurs earlier thanks to my treatment there is no problem at all since you are no more”. The patient laughed and asked me”If I change the Rheumatologist what will happen ? “I replied “If you do so the last two possibilities will occur earlier and I will live longer”.🤣How can any doctor guarantee how long one should take treatment for a chronic disease which outlives the Doctor 🤣