Go for it OP. FWIW, my Mother is 55, and has several body-con dresses in her wardrobe (mid thigh, yes, but always with long sleeves, a higher neckline and 120 denier TS tights, for balance), as well as lots of skinny jeans etc. She had a fabulous (toned size 8) figure, killer legs, not a trace of cellulite and is bloody beautiful, and virtually wrinkle free, to boot.
She is one of the most stylish women I know, never looks like mutton dressed as lamb (or indeed a 'slut', which incidentally Polly, is a horrid way to refer to any woman), and is always classy looking. She sometimes frets that she ought to dress more 'age appropriate', ie, like my somewhat frumpy aunts. Bugger to that, I say. Her gorgeous clothes make her feel good, and I personally believe that, in part, her vivacity and fun loving attitude are down to her dressing in a way that makes her feel younger (not saying people who don't dress like her aren't vivacious or fun loving, just that it seems to work for her).
Sorry for going off on a tangent there OP ( I think my Mum is fabulous, can you tell?!), but what I was trying to convey was, age means bugger all! If you can pull it off, and have the confidence, wear whatever you fancy. Enjoy it, don't let anyone tell you that you ought not wear whatever it is that makes you feel good, and remember, there is plenty of time for conservative when you are 85!! 