Yahoo to keep personal search data for 18 months instead of three

Yahoo said it would begin keeping records of its users search engine queries for at least 18 months, not three in an effort to "keep pace" with what its competitors are doing.

Microsoft keeps search data for 18 months, too.

Source:
http://latimesblogs.latimes.com/technology/2011/04/yahoo-keeping-personal-search-data-for-18-months-instead-of-three.html