So help me understand: Why do experienced divers carry long hoses and why do tech agencies emphasize gas sharing practice? You suggested earlier it had to do with being comfortable with your buddy's skills. This makes sense if you are insta-buddying, but most people I know frown on insta-buddies and dive with people they know very, very well. They don't need to do an S Drill together to be confident in each other.
And in addition to carrying a long hose, many serious divers avoid placing deco bottles on their RHS to keep the long hose free. This seems like an awful lot of bother if donating gas is just an optional nice-to-have with no real necessity for a diver to rely on their team for gas.
And further, if it is just a temporary breathe off it while sorting out the issues, why make it a long hose? The long hose is presumably so that both divers can share gas all the way home or all the way to where they can switch to deco gasses or pick up bottles left in the cave.
Just a n00b asking questions here... But all this emphasis on the long hose and air sharing amongst some very experienced divers makes me think that there are people who place a certain amount of their trust in their buddies for more than just a nice-to-have comfort factor.
That may not be you, of course.
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