I think it makes sense to not leave clamped for too long. This is just an engineer's educated guess, but when you clamp the wood is compressed, and when you release the wood expands. So releasing the clamps when the glue has set, but may still have a tiny bit of flexibility, seems like a good idea.

In other words, clamping pieces together induces stress, and relieving that stress once the glue has fully cured will put that stress into the glue joint.