Helzberg Diamonds online marketing manager Lisa Dick said too much testing on email content effectiveness can wear out proud designers. She said you can suck the soul out of them, "so you really need to be mindful and respectful" that you're trying to do your job and they're trying to do theirs. "They will quit if you suck out their soul and tell them too many times, this isn't art," she said. But Brian Brown of ideapark said there are business goals and "branding guidelines within an established set of what we can do," so there are limits. "Not every designer is set out for this because they can't take it," Brown said. An Expedia executive said the company invited designers into discussions about creative testing and found there were a lot of things they wanted to test, so collaboration is key