I agree about mouth dumping the loop pretty much tells you when it needs to come out. Additionally letting the gas slip from the corner of your mouth doesn't obstruct vision as much as purging from the nose and doesn't dislodge the mask.

As far as the "OC tech" comment I suspect he means that with limited gas supply you want to make use of it before getting rid of it. After all you carried it all that way and then to just release it in the water is a waste. May as well get some fuel for the body before letting it go. Of course that doesn't take into account being at the wrong depth for the mix.