The most benefit will be derived by running Active Recovery within 3 hours of finishing your workout. Beyond this, any metabolic waste that is left sitting in the muscles will have already done its damage. In order for the muscles to recover as quickly as possible metabolic waste needs to be flushed out, and fresh blood and nutrients need to be delivered to the muscle cells as quickly as possible. The longer this process is delayed, the slower the recovery process. If it is not possible to run Active Recovery within 3 hours of finishing your exercise, you may still run Active Recovery at any time. It just won't be as effective as it would be if ran 3 hours or less after your workout.