Currently, collected data immediately undergoes a "de-identification" process that separates account information (a name or email address for instance) from non-personal information (such as your search query). After 18 months, your IP address and any remaining cross-section IDs are deleted.
Instead, Microsoft will simply remove IP addresses after six months rather than a year and a half, but the rest of the process will remain intact, as the company uses the data to improve its product. The new policy will take effect over the next 12 to 18 months.
Google currently anonymizes search logs after nine months, and Yahoo after three months.