Ongoing multivariate testing is certainly a thing, especially in high volume e-commerce, and especially on ad company's advertising-related UI. You're correct,

Ongoing multivariate testing is certainly a thing, especially in high volume e-commerce, and especially on ad company's advertising-related UI. You're correct, winners are chosen and rolled out (to the majority) but then new tests are created against that winner, and that's an oversimplification.