The short answer is that gift certificates and vouchers for a specific service are allowed to expire, but should clearly indicate the expiry date on the voucher or certificate itself. This may be more common where services like a massage, manicure or oil change have been donated for a charitable event or won at an auction. As long the company offering the free or discounted service makes the conditions and expiration clear then it is allowed to have an expiry date on it.

Related questions: