As a Conversion Rate Optimization consultant I couldn't agree more. We have specific domain expertise and our clients need us infrequently. We also have a large

As a Conversion Rate Optimization consultant I couldn't agree more. We have specific domain expertise and our clients need us infrequently. We also have a large library of wins and can quickly help them get into the high performance zone (and dramatically increase revenue) without them directly incurring the time and expense--A/B testing is expensive from a media buying perspective. But we eventually hit diminishing returns and at that time it is best to end the engagement and move on. If you are curious, here's a case study: https://moz.com/blog/cro-case-study https://moz.com/blog/cro-case-study