A Flight Review is required every 24 calendar months by the FAA for all pilots who intend to act as Pilot In Command. Although the requirement is to complete a flight review every 24 calendar months, the FAA encourages all pilots to complete a flight review as often as needed to maintain currency and safety.
There are many other activities that qualify as a flight review (examples: FAA sponsored pilot proficiency programs, passing a flight test for any certificate or rating, completion of any phase of the FAA WINGs program). If you have not completed one of these, schedule some time with a friendly Twin Oaks instructor and airplane and get your Flight Review done quickly and easily!
A flight review is required to be 1 hour of dual flight instruction and 1 hour of ground instruction but most pilots will spend 2.5-3 hrs. It will be a review of the general operating and flight rules of Part 91 as well as a review of maneuvers and procedures in the airplane that are necessary to demonstrate the safe exercise of the privileges of your certificate.