Fat Transfer Face How Long Before the Fat Settle? Why Do Some People Loose the Fat After a Year?

I don't understand why some people loose the fat from a fat transfer in face after a year cause the fat whats left after 3/4 months should be permanent and then the fat should settle. So how can some people loose the fat after a year while the fat should be a part of the body at that time and should be hard to loose cause fat is hard to loose.