Typically you have a year to complete a class. However individual instructors, before they take you in the ocean, may require more extensive pool and classroom reviews depending upon how long it has been since you completed those modules. These skills need to be fresh in your mind and muscle memory so that you dive safely and have an enjoyable experience. Your referring instructor and your recieving instructor should be in contact regarding your progress.
This is really good advice. If your instructor does not require it, I strongly suggest that you request a refresher session.