I think aging is not a matter of bones or skin, it's bone, skin and everything in between: muscles, retaining ligamengs, fat. It's a multifactorial thing that experience aging as time goes by. My own obsevation also is that aside from the sagging issue, our faces lose fat in some places but gain them in others, changing the entire face shape with time. Grafting some fat in the places where it's been lost is not enough as there are some places where the fat hypertrophies such as the double chin. It's all one giant clusterf**k and our best bet is for us to slow it down as much as we could with nutrition, supps, lifestyle...etc because so far no doctor can make a 50 year old pass as a 20 year old, and judging from the path anti-aging plastic surgery is currently taking; I don't think it's happening anytime soon, either.