I have pellets implanted every 10 months. They are more expensive than pills and shots and my endo takes care of that every . . . well, every ten months.
I switched because they (according to my Dr) are the least problematic delivery system, after implantation (takes about 15-20 minutes) is taken into account. I have a day of mild, very localized soreness and wear a large bandage for 5 days. I'm post-op, 11 years, and I really like the pellets.
Hope that's helpful,
R