I'm 40 (although I look ten years younger) and am more interested in fashion now than I ever was. I think whatever age you it's about finding that balance between fashion and style that works for you. The important thing is that YOU feel comfortable and confident in what you wear and you'll have more chance of carrying it off. If you look in the mirror and find yourself thinking, 'can I really pull this off?' the chance are you won't.
I've always walked a line between fashion and timeless style that works for me and some of the recent trends absolutely suit the more distinguished older gent down to the ground (I'm rocking the heritage look, tweed, brogues, fair isle, chunky knits, chambray oxford shirts and the like at the moment). And with oldies as models is all the rage, never has being old been so fashionable!
This summer I went to town on block colouring (bright red and blue chinos and loafers/espadrilles were my uniform) and breton styling, fairly on trend, but done my way (a smart tailored edge to the casual).
I can't comment on the carrot cut chinos as I'm not a fan of them on anyone, but I can stil carry off a skinny cut with the best of 'em I like to think.
So, be confident, wear what you feel like, blur the line between style and fashion and don't listen to others' opinions too much.