You can hurl many insults at fashion but ageism isn't one

Fashion has an undeserved reputation for all kinds of faults – sexism, elitism, chauvinism (I was once accused of the last of these when I criticised Italian design; they evidently hadn't read what I'd written about London that season). Ageism, however, is possibly the one most often tossed about. A designer recently told me that he thought it obscene for a 16-year-old to wear an €11,000 sheepskin jacket: he preferred a more believable 21-year-old billionaire with a taste for deluxe Del Boy chic.

And yet, last week, when the announcement came that Grace Coddington, creative director of American Vogue magazine, would be stepping down from her role, the question on everyone's lips was “what next?”. Coddington has found new representation with the New York agency Great Bowery, and her role at American Vogue will continue: she will shoot several editorials a year and retain an office at the magazine. “I'm certainly not going into retirement,” said Coddington, with trademark candour. “I don't want to sit around.”

Grace Coddington is 74 years old: imagining someone of her age stepping down from such a pivotal role in any industry is easy, even understandable. What is remarkable is that the stepping-down is actually a mark of gearing up for new challenges and experiences. Fashion is full of that: witness Suzy Menkes, now 72, former fashion editor of The Independent and, for 25 years, the fashion voice of the International Herald Tribune (now the International New York Times). Aged 70, she left to join Vogue, now reporting across its digital platform to multiple international editions. She has voraciously taken to Instagram – over Christmas, she spontaneously reviewed the holiday window displays of various retailers.

Elsewhere, Karl Lagerfeld is 82, Giorgio Armani 81. Both present new collections this week as part of Paris's haute couture week – Mr Armani has presented two already this month. There are no signs of abating. Carmen Dell'Orefice is a model who turns 85 this year – photographed by Penn, Horst and Avedon in her youth, she is still working (although lately this is because she lost her life savings thanks to Bernard Madoff's banking fraud).

I suspect fashion's ageist reputation comes from the fact that, bar exceptions such as Dell'Orefice, most of fashion's most public faces – namely, the models on billboards – are young. Behind the scenes, however, it's the powerhouse of knowledge and respect that age brings that helps you to assert your place in the industry. Furthermore, one imagines the constant change and endless renewal of the industry not only motivates but encourages you to try something new. I hope I've still got that fire and curiosity in 40 years' time. I also hope I've got the money for that sheepskin coat.