Understood.
Also agree that I may have gone to 100' back then with a J valve if it was set to a higher break value.
Thanks, now I know exactly where the " keep 100' PSI for every 10' you have to ascend" (ie. 1000 for 100') comes from.
So, if you are another who would plan to use the air the J Valve releases as part of your ascent plan (though not if it releases only 300 PSI), this leans me more toward not calling that gas "extra".
The Cousteau writing and the 1968 article explain what the valve is and does and how it works (we all know that). They don't explain if it was intended to be used on every dive or not.
Dove a U.S. Divers steel 72 with J-valve and a single hose Voit Avalon regulator from 1965 to 1974 in both OW and overhead environments. When in an OW environment, we would routinely use the J-valve on ascent from medium depth (40-50ft) or while playing around in the shallows. We were always out of the water before any OOA situations. However, when in an overhead environment, which was most of our diving, we never planned or used the J-valve for anything other than an emergency. In overhead environments, if we had to pull the rod, we would have seriously screwed up our dive plan. We were ultra conservative divers, so that never happened. It is also important to remember that back in the day, if you had to share air, it was buddy breathing, not sucking on an octo, so we would not be down at 90-100ft anywhere close to having to use the J-valve for ascent.
Edited to add: Also, our fill guy was a man who filled the fire department's tanks, and he would routinely fill our tanks to 2600 psi without us even asking for a 10% overfill.