Lewis is right. I have had an Epcot after 2 ticket. It was given to me at a convention. I don't recall if it had an expiration, but I know the tickets that DIsney sells to convention goers do have discounts so this one might also.
And it really isn't a great deal financially either. It costs $40 (maybe a couple of dollars more with the recent price increase) at the conventions. A full day is only $15 more.
We are going with some friends in July and they are offering her husband's company after 2pm convention tickets and it states very clearly that they DO expire. I would be very leary of buying these tickets off eBay. HTH.
Lisa