Your campaigns need to be managed and optimised regularly to make them work better over time, and allow you to expand on them.
This involves creating new ad groups and keywords, pausing ads or keywords that aren’t working, making suggestions about new campaigns, checking if the budget is adequate and making suggestions around where to increase it, ensuring your ads aren’t being shown for irrelevant keywords and lots more.
The advertising space isn’t static. There’s millions of calculations performed in a real time auction every time an ad is displayed. Optimising it means your campaigns will continue to improve and expand. Even if nothing was touched, and other advertisers started new campaigns, your results could be very different on a week to week or month to month basis.