Inside AdSense: Save your top queries

Now your adsense for search reports will be removed if they are older than a year. If you want that any specific report not to be deleted you should save them before December 10th.After that all the earlier reports will be deleted.
This step is taken by google to remove unnecessary data in their servers.

See this pic:


As quoted by adsense:
IF You use adsense for search i shall let you know about an upcoming change on December 10th that will affect your top queries reports. To prepare for a few upcoming reporting enhancements, 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.
Inside AdSense: Save your top queries