The results immediately following surgery will be the largest due to swelling and lack of fat resorption. The buttock will continue to decrease in size for the first few weeks. After the first 6 weeks, the result is stable and permanent. There are studies to document long term retention. For the BBL, about 50 to 70% of the fat survives long term. I have seen patients after a year or two, and the pictures reveal that the gain is permanent. Perhaps this is due to injection technique, harvest technique, amount transferred. Find a board certified plastic surgeon who performs hundreds of BBLs each year with favorable patient feedback and hundreds of before and after photos of his or her artistry.Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA