Vent: people keep gluing the spine before the text block is pressed flat

I keep seeing folks in my local bindery group glue up a case binding while the text block still has a slight bow, and then wonder why the boards warp a day later. Last Tuesday a guy brought me a journal he made in a class at the community center in Tulsa, and the front cover was already curling away at the fore edge. The culprit was simple: he glued the spine in one pass and skipped pressing the block flat for even 20 minutes first. I press mine between two boards with a couple of bricks on top for at least an hour before any glue touches it, and I have not had a warped cover in about 40 bindings. The glue pulls as it dries, so any curve you leave in the paper just gets locked in. Does anyone here press longer than that, or am I being too careful?