How much data (i.e clicks, impressions,and other metrics) should be collected before you can use this information to spot trends in your campaigns and keyword performance. I hope this question makes sense... Thanks
You probably need at least 7 days, to cover the monday to sunday spread. As some industries perform better on Weekdays than on Weekends. Others perform consistently across all days. To be safe, I'd run the test for 14 days or more. Usually the more data you collect the better your decisions will be.