I'm 47 and stopped wearing shorts around 10 years ago. (Not counting "gear" shorts - for exercise, boating, hiking, etc. That's just plain practical). I actually have decent legs, one of my best features, no cellulite or varicose veins. Proportionately, I rock the shorter lengths quite well (whereas bermudas look horrible on me). So why did I stop wearing them?
Because I had to face facts that the skin on my legs just wasn't looking all that great. All the tone in the world doesn't make up for saggy aging skin (reference that Demi photo; and I bet JA's photo has been shopped). Also to be honest, the older I get, the more icked out I am at the thought of putting my bare leg on a public seat. Maybe that's weird. Maybe I'm becoming my mother!
Would I wear winter shorts with opaque tights? No, for the very practical reason that if it is cold, I want more coverage than that. For similar reason, I only have two winter mini skirts left in my closet and neither one of them have been worn in a long time. The last time I wore one was for a Halloween costume, in fact (which is why I've held on to them).
When I think about it, it's not so much how I look, or worries of mutton. It's more about how I feel inside these days. As I get older I am more practical and choose comfort I guess. Even if I lived in a hot climate, I find loose flowing dresses more comfortable. Besides, my legs have been exposed to enough sun by now.