Announced in the Google blog by Peter Fleischer, global privacy counsel, the Google PREF cookie, that stores your settings and preferences for Google, will auto-expire after 2 years.
This compares to the original design of the PREF cookie which had an expiration date on 2038.
"In the coming months, Google will start issuing our users cookies that will be set to auto-expire after 2 years, while auto-renewing the cookies of active users during this time period."
"In other words, users who do not return to Google will have their cookies auto-expire after 2 years."
"Regular Google users will have their cookies auto-renew, so that their preferences are not lost. And, as always, all users will still be able to control their cookies at any time via their browsers".
So, with the new policy, every time you log on to Google, the 2-year expiration starts again on a rolling basis. You will obviously still be able to delete this new cookie via your browser.