I think you are asking about the little coupon book you pick up at the Monorail station? Is that it?
If so, I've had those little booklets before, and they DO have Exp. dates........if not on the individual
coupon, I think its on the booklet.
Otherwise, the Monorail Ticket itself, is what Tanya explained.
Best place I've found Monorail discount tix in past........is IF theres a Convention in town during your stay,
(and theres almost always a conv. in town) you can usually find a Monorail Link on the Conv.
website offering Discount Monorail Tix.
You need to plan in advance though, because after purchasing online, the Discount Monorail pass is Mailed to you.