Your results will be long lasting so long as you maintain your body weight following surgery.
The ageing process will however continue from your new post procedure point, and skin laxity will gradually increase over time. The ageing process will start from a far better point however, so it should be many years before this becomes noticeable again.
As you get older, however, you should expect to see the buttock skin begin to sag again, particularly if you gain weight
A Brazilian Butt Lift, otherwise referred to as a Brazilian bum lift or Brazilian buttock lift, is a cosmetic procedure that involves the transfer of a large amount of harvested fat to the buttocks to create a fuller-looking bottom.