We find whenever we significantly change the look of our website or our emails, conversion goes up significantly for a couple of weeks and then most the time go

We find whenever we significantly change the look of our website or our emails, conversion goes up significantly for a couple of weeks and then most the time goes back to the normal levels. I think a difference just stimulates the brain, along the same lines of why supermarkets infuriatingly keep moving the products around so you can't just auto-pilot your shop.