In most cases, the swelling and fat resorption in a Brazilian butt lift will subside by 6 weeks post op. By this time the remaining fat should have established a good blood supply and should remain indefinitely. Since this is your own fat and will respond as your other normal fat cells do, if you gain or loose weight. Best wishes, Dr Lepore.
It is impossible to give you an accurate answer because "it depends". Unfortunately some patients lose volume continuously and will need a revision. In my opinion, this is caused by poor surgical technique and is the reason why anyone seeking a BBL needs a true expert who specializes in this procedure. I perform 6-8 BBLs per week and tell my patients that most of the volume loss will be in the first 4 weeks. My patients rarely see any significant change in the buttock size after week 6. This volume should then hold steady FOREVER! This is only my personal experience based on my personal technique. Obvioiusly, every surgeon will get different results. Speak to your surgeon