When I used to play Rift, I did so before it went F2P, even preordered. They gave players who preordered the option of a unique discounted monthly subscription ($13.99/mo I think) with the caveat that canceling your subscription for any reason voided the ability to re-select the discounted rate later.

I was really hoping to see an option like this when they finally opened up the subscription plans for ESO... such sad. -_-