On a Federal level, OSHA cards do not expire so long as you still have the card. For information on lost/stolen/damaged cards, click here.
New York, Pennsylvania and Connecticut do, however, have a state regulations that require recertification every 5 years. As there are no OSHA 'refresher' courses available, recertification requires the purchase and completion of an entirely new, full length course.
For example, if a course was completed in June of 2011 and you still have the card, as of July 2016 it would be rejected in New York, Pennsylvania and Connecticut but would still be accepted in all other states (aside from California which has its own regulations).