Google AdSense blog post: ….top queries data older than a year old will no longer be available. In other words, you’ll only be able to view top queries reports dating back one year from the day you’re generating the report.
If you have important top queries data which are older than a year old, please run any appropriate reports and save them before December 10th. You may also wish to generate a report dating from the date you started with AdSense for search to today, as data not within the one year window will be continuously removed.
Google, AdSense, AdSense Search, Top Queries, Earnings, Report, New Features