Will I have to use Minoxidil 5% and Finasteride for the rest of my life?

Finasteride and Minoxidil are lifelong therapies offered to patients to maintain the existing hair. If the medication is stopped, hair loss often follows.

Balding is progressive. Keeping the original hair that you have is just as important as adding the transplanted hair. I strongly recommend lifelong medical therapy for nearly all of my hair transplant patients. 

Once you start usually hair loss products, you do have to use them for the rest of your life for them to continue to work.  If you start and stop, the hair loss will just continue.  It is totally up to you but I recommend a good aggressive form of maintenance therapy to ensure that you keep your existing hair.  What you don't want is to keep getting surgeries to chase hair loss.  

You doctor is advising you that you have a progressive problem (that is the nature of genetic hair loss) and taking medications will slow the progression.  To do this or not, is your call.