Creating an image for a brand and truly embedding it in the life of a consumer takes investment not just in renovation but in the relationship — between brand and individual, and designer and brand. After all, the products themselves require investment. They are not cheap. Consumers have to believe they will hold their meaning over time. And the meaning is created by the designer.

Modern luxury theory has it that the brand has to be greater than any individual, but we should not forget that brands are given their personality and their depth by the people who make them. They aren’t caretakers; they are content creators (and not in the social media meaning of the word). Comme des Garçons is Comme des Garçons because of its founder and designer, Rei Kawakubo; Ralph Lauren because of Ralph Lauren; Giorgio Armani because of Giorgio Armani; Chanel because of Coco Chanel and now the designer Karl Lagerfeld.

Indeed, though the latter did not create the style of the maison he took on in 1983, he has worked within its vernacular for over 30 years. As a result, it is still clear what the brand stands for, and you can buy into that value system or use it to telegraph your own. Similarly, Maria Grazia Chiuri and Pierpaolo Piccioli, creative directors of Valentino since 2008, have succeeded in establishing a modern character for the company that speaks to the legacy of its founder, rooted as it is in beauty and decoration, while also giving it a resonance in contemporary culture by combining a certain rigor of line with elaborate craftsmanship. But it has evolved over seasons — their first few shows looked very different — and if they had departed after Year 3, their contribution would have had very little impact. It would have been a blip, rather than an identity.

If the value system a brand represents changes, and changes very dramatically, as it did at YSL under Mr. Slimane, who crushed its botoxed Le Smokings under a highly merchandised California youthquake truck, it: a) takes a while for the world to adjust (remember the initial shock! horror! at his grunge grrls on the runway in Season 2); and b) can give consumers whiplash if it then segues into something else entirely.

As to what might lie ahead, at least for YSL, rumors are centered on Anthony Vaccarello, a young Belgian-Italian designer whose last show was very 1980s rocker — in part because it doesn’t seem a huge departure from the Slimane aesthetic, though it is more aggressively sexy and less holistic. Kering said it would make an announcement “in due course.”