Sophie had a fat graft to fill out her hollow cheeks a few years ago. It was definitely a big improvement. From what I remember, your face looked fairly youthful, so if you are considering it, I don’t think you would need much, or might want to consider a temporary filler, just to see how it sits and give you an idea of how it might look. Which areas are you considering? Full face?
The fat has a very high chance of reabsorbing, it’s inevitable, so the question is how much will reabsorb. When my Sophie got it done, she had to go back for a follow up treatments (2 to 4), and most clinics here save your extra fat for follow up injections. I believe they can save it up to 6 months. Not sure if that time limit is for scientific or business reasons.