Well, I guess we can't draw blood on our wee ones to evaluate their vital functions....Maybe one day?
But, I love the science of Ichthyology! I have the coolest PM relationship with one of the curators of a large public aquarium (I love you, Jim Hemdal and everyone should buy your book/shameless plug for Advanced Marine Aquarium Techniques!). Really, Jim does surgery on his fish, he puts them under sedation and uses little tiny ventilators (a syringe) to help them breath during surgery!
So, I really have put some thought into the vital organs of our captive pets, and every parameter I can test for. I do understand there are differences in the water the fish is transported in and the water that he is being transferred into. The major electrolytes (Calcium, potassium, magnesium, ect) are controlled by the fishes internal mechanisms and are a non issue to me. A fish that is breathing and has circulating blood will be able to control these parameters. But, elevated ammonia in the transport bag will cause chronic lung dysfunction. I am not sure that gill tissue ever heals from a significant burn.
Granted, hopefully the fish has only been in a bag for a short time and the water isn't too toxic. But, I see no valid reason reason to leave the little thing in a tiny bag for more than 20 minutes when he could be in a lovely tank, checking out his new digs and finding a way to calm down after a freaky stressful experience looking at a terrestrial world in a plastic bag!
Everytime I bring a bag home from the LFS, I think how bizarre it must be for the fish. When we take the bag out of the sack and he is in our front room looking at Lou Dobbs on CNN, the huge eyes on the dog looking at him, even my huge hands that are bigger than his whole body! That must be way more shocking than any change in water quality (for the better, IMO)
I do know that there are many places where we can read that longer is better, but I have yet to find one that says why? If we were going from a good environment to a more stressful one, it would make sense. But, we are moving from a potentially toxic one that we have worked hard to make healthy. So, why would we go that slow? Over an hour and a half?