I'm 48 and like you, spent many years yo yo dieting. I've kept the weight off for several years now. I strength train regularly. The skin on my arms did pop back. the skin on my stomach didn't. That's just the way the genetic ball bounced. As we age, our skin looses its elasticity. So, the younger a person is when they lose weight, the better the chances are that the skin pops back.
Not to be nosy, do you smoke ? Smoking reeks havoc with our skin. It ages it beyond belief. If you don't smoke, that's going to help. Do you use sunscreen or wear a hat ? Staying out of the sun also helps keep our skin young. little things do add up.
the fact of the matter is, when a woman reaches a certain age, things do start going south of the border.
Strength training can help. How ? When you have strong biceps, no one will care if you have a little sagging skin or not. They'll just be in awe of your amazing guns !!