I tried that once & wouldn't recommend it. Among other things, I ended up with some seams that had to later be either un-done or else pressed with a wrinkle in them & quilted down (I tried both & they take nearly equal amounts of time & aggravation). I actually like ironing, but didn't want to disrupt my "flow" to be constantly getting up & pressing seams. I had to learn the hard way that there is a reason our sewing teachers taught us to press as we go. You might get away with it once or twice or ten times, but if you're like me, eventually, over the course of 50 or so seams you will have one or two that get away from you ... and of course those will be the ones dead center in your quilt top.
It truly is, in my humbling experience, worthwhile to press every time you've joined a seam before you add another piece of fabric (even if that piece is on the opposite side).