My opinion on Fat Transfer
i'm glad you asked.
i do not like fat transfer and i do not do it.
no matter what anyone says about their magic, super-duper way of processing the fat and how it lasts forever if they do it, fat is unreliable.
it can last a few months or it can last a few years, and no-one can tell you ahead of time what's going to happen.
the other problem with fat is that it is not that precise, whereas you have to be super precise for the lips to look good and natural. you never want to lose the cupid's bow of the top lip or the gentle curve of the bottom.
i have been injecting restylane and juvederm for a long time. they are both super precise and i find that juvederm ultra plus lasts longer than restylane by a few months (about 7 to 8 months total).
i've seen that, after a few sessions, there is collagen stimulation that tends to last, so you tend to need the injections less and less often.
the same points apply to nasolabial folds
hope that helps