It totally depends on the person.
I am 40 years old, gained and lost lots of weight lots of time, had six pregnancies, got MAJOR stretch marks and a HUGE waist and hips, got above 280 pounds for awhile, stayed morbidly obese for about ten years of my life and am down to 203 right now.
I do have some saggy areas but they still have plenty of fat attached... thighs, upper arms, and hip area. But the skin thing, I took it seriously. I read all the posts and heard the naysayers who told me nothing would help skin shrink, and decided to do whatever I could to get the best result possible.
What I do:
dry skin brushing (as detailed, I think, in the above links) a couple times a week
take omega 3 supplements
use good moisturizers, every day (I rotate between whatever is on sale... firming lotions, body oils, alpha hydroxy lotions, whatever... and I massage it into trouble areas, especially my waist).
I think it is helping. I posted a picture of my naked waist
here in this blog post.
Just do the best you can and whatever happens, happens!