Keeping Event Logs

Depends on your company policy and security issues. If there are none and it's up to you, then I would look at what information is in the logs and how often I refer back to the event logs for problem origination and determination.

I would recommend that you rotate 2 months listings, but depending on the size of your organization and what is recorded in them, that may not be feasible. When our logs grew too big, I reduced that backup to 1 month and kept printouts of the logs when specific events occurred.