I think an experienced rational diver would use the Spare Air to calmly get to one of his or her buddies who should be around the same depth and less than 45 feet away and commandeer their occy. This "race to the surface" mentality is just plain silly when there is a larger reliable air supply nearby.
You shouldn't need a RAS to get to your buddy's octopus. All you should need to do is tap or flash them, signal out of air, and have them pass you one of their second stages.
If you're "same day, same ocean" kind of buddies, then you're both solo diving, and should both be equipped for solo diving.
If you were separated by accident, follow the buddy separation protocol.
If you dive "same day, same ocean" without being equipped for solo diving, it's even more imperative that you head for the surface and not for your buddy. It's not like you were going to complete the dive plan on your buddy's octo, is it?
Let's dissect this example further, just as one possibility.
Chasing after your same-ocean buddy's octo on a spare air introduces several risks that weren't there before:
* In addition to stress, you begin exerting yourself, raising your oxygen consumption rate.
* The spare air might fail due to lack of maintenance, or run empty even sooner than expected.
* The spare air is held with your teeth, so it's possible to drop it and have it float away.
* Your oblivious buddy might swim away from you, adding too much distance to cover.
* The #1 reason for OOA being inattention to the SPG, your buddy might run dry just as you're managing a shared air ascent on their octo.
Having performed these exercises, as the few breaths from the spare air end, you risk being not only out of air, but also low on blood oxygen - worse off than at the beginning.
And what risks have you mitigated, should you succeed in chasing down your buddy?
* Skipping the safety stop slightly increases the extremely small risk of DCS. Rec diving is done within the NDL, specifically selected so that you can always ascend straight to the surface.
* If your buddy has enough air and you have and know to use your SMB, you'll have reduced a fairly important risk of being struck by a boat.
Having a spare air is always better than having nothing at all. But where it can be
worse than nothing at all is in promoting the kind of thinking that relies on it. The only safe way to dive with a spare air is to dive as if you don't have it, until the last moment, when you're either out of danger or out of options.
A safer course of action would be to keep your regulator in your mouth, signal OOA to your buddy, and begin a slow methodical CESA. If your buddy can get to you quickly, use their octo. If they can't, signal them to shoot up their SMB and ascend. If you are still getting some air from a freeflow or from reduced ambient pressure, use it. If, approaching 20-30 feet, you still have some air, keep using your regulator, else use your Spare Air. If it works, breathe out into your SMB to deploy it, otherwise look for boats and ascend.
This isn't some universal procedure, of course. For instance, in rough waves, it may be better to keep the air reserve for the surface than for waiting. If there's very little boat traffic, or if you're not familiar enough with SMB deployment to do it under pressure, it goes down on the priority list. You always have to think. But what makes this plan acceptably safe is that it doesn't depend on any convergence of more things going right. If you get air from your buddy, time to deploy your marker, air from your spare, etc, you use them, and if not, you still get to the surface.
. Now, I mostly dive...solo diving, some of the same feelings, just shorter and less strenuous
