reasons for laminating the top
I had started gluing up 2 layers of 3/4" MDF for a table top. I got side tracked and couldn't finish so I put it up for a while (almost a year). When I finally got back to start putting the oak trim banding, the top was not flat. The front was flat but the back side had a 1/16" sag on both outer edges. I sanded it flat before adding the edging but after attaching the edging it was again off because I cut the edge strips a hair less than the 1 1/2" thickness of the top. I just could not recover to my satisfaction so I gave up and bought a top from Rockler that was on sale.
The point I am trying to make is that MDF will move, swell, whatever if you don't wrap it up tight. I believe that you can't be too cautious and should laminate both sides and soon after gluing up the layers.