In May, Google made some changes to how ad rotation works in AdWords, changing it to a 30-day period, at which point AdWords would optimize to show higher performing creatives. After some users expressed concerns, Google announced today that it has made some adjustments.

Google says it will expand the even rotation period from 30-days to 90, so there’s a longer testing window for new ads. Google is also offering an opt-out option, so advertisers can continue to have their ads rotate evenly indefinitely.

VP, Product Management Nick Fox writes on the Inside AdWords blog about why Google updated how creative rotation works:

With the modified Rotate evenly setting, our tests indicate that we will provide you with more valuable traffic in an automated, efficient manner. We’ve found that, on average, optimized creative rotation results in an increase in click-through rate and an increase in total conversion volume for advertisers. Here’s an example describing the benefit (note: data is intended for illustrative purposes only):

Advertisement A has a 3% CTR, while Advertisement B has a 1% CTR. Under the original Rotate evenly setting, the ads would show roughly evenly, resulting in an average CTR of around 2%. Under the new setting, Advertisement A will show more frequently after the even rotation window has passed, bringing the average CTR closer to 3%, or a 50% increase in clicks. Our systems will also continue to run Advertisement B for a low fraction of traffic to continue to test how well it performs.

If you want to opt-out of the rotation setting, there’s a form here. Changes will go into effect on June 11. Google says it will offer an opt-out option right in the AdWords interface if there is high enough demand.