Sumner County has seen enough casino proposals that it has learned not to get too excited by fancy artist renderings and developer promises. Still, the third time may finally be the charm in selecting a developer that won't pull out. One of the developers is Harrah's, which two years ago won the bid to build and operate a state-owned casino, then backed out when the economy fell apart. But Harrah's and the other two developers appear committed to the project this time. Of course, that's what we thought before.