Be bold!

I realise that it is tempting to opt for safe fashion options once you are past 40. As I was answering Mary's comments on my post on vintage, I realised that my feedback to her question on skirt length might come across as rather tame and I want to quickly dispel any notion that safety is what we should aim for at 40+.  Invisibility is what threatens us as heads no longer seem to turn as we walk into a room, so we should not give in to the temptation to simply politely fade into dull greyness! It is quite cruel to feel invisible when we once felt we existed in other people's eyes but maybe it is time to look for another form of reassurance: the confidence that we feel good in our own skin, that we know who we are and dress accordingly. Boldness in that sense does not mean a sombrero and gold platform shoes, but a style that is really ours, that suits and flatters us, that we wear and does not wear us and allows us to express our individuality.

So, to come back to Mary's question on skirt length, my recommendation to aim for knee length does not mean boring and old-fashioned. It means being practical and hiding knees and thighs that might not look great at 40+. A few of examples taken from Nicole Fahri's autumn collection show that knee length can also mean elegant and feminine: a flared boiled wool skirt a £160, a silk sateen piece at £290 and, going up a notch in price at £400, a silk bonded number in bright green on the picture and also available in a beautiful pink in the shop.  They are not cheap but it might make sense to invest in a few beautifully cut and made items that will last and are versatile enough to be matched with cheaper tops.
http://www.nicolefarhi.com/category/1/Nicole+Farhi+womens+Skirts/Skirts.htm

Still on the subject of skirt length, the vexed issue of the miniskirt finds a nice interpretation in the shop-window of Anonymous by Ross & Bute in Ledbury road, London W11.
http://www.anonymousclothing.com/home

The long fluid cardigan, the high boots and the short skirt work well together and present a sexy look without being slutty. What's missing is the thick tights which would finish the look nicely for a 40+. There are plenty of long cardigans and knitted coats to choose from in the high street and in designer shops.

Another answer to short dresses or skirts is leggings. They can hide a multitude of sins but should be worn appropriately. More, the US magazine that targets 40+ women has a very good summary of how to wear them:
http://www.more.com/2013/8491-leggings-after-40--dos-and