Yes, the block out ticket is only good for a single day (and I think it might only be good on the day of purchase, but that I'm less sure about). It is a park hopper, so that's nice (and a pretty good savings from the standard 1-day/2-park ticket).
If you use today's prices, it costs $170 to upgrade from the Deluxe to the Premium. So it slightly more than 2 block out tickets ($168). In the end, I think with parking included and the slightly higher discounts on food and merchandise, if you have to buy two block out tickets, you might as well upgrade the Deluxe.