Loose skin after weight loss

So there is this guy at my job who has really inspired me to lose weight. He is down to 278 after losing a whopping 72 pounds already. He has done it by eating the Nutrisystem meals. One thing he just told me is that by losing so much weight so fast he is seeing some "loose" skin in places. Does skin lose its elasticity after being stretched out so long? If you lose weight slowly do you give time for your skin to shrink with the fat under it? Or is it a fore gone conclusion that if you are big now and want to lose weight your skin will remain loose afterwards?? I started at 304 on a 6' frame and have lost about 20 pounds but wonder if I should slow down and lose this weight slower??