Found this in their privacy statement:

Why are logs kept before being anonymized?

We strike a reasonable balance between the competing pressures we face, such as the privacy of our users, the security of our systems and the need for innovation. We believe anonymizing IP addresses after 9 months and cookies after 18 months strikes the right balance.

So they tie your search to your ip address and keep it for 9 months, and they keep cookie data for 18 months.

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