I know a couple of DIR divers and they are at both ends of the spectrum.
The first one dives DIR *ALL THE TIME*, the second one dives whats best for the conditions. On a shallow lobster hunting dive one of them wears doubles with a long hose, the other wears a single.

DIR is a great system (many systems are) but like any religion you need to temper it with common sense based on your situation. For example, I dont cave or wreck dive, so I would NEVER use a long hose, the reasons DIR give for a long hose don't fit my dive style. If my buddy is OOA and needs to air share I dont WANT him 7' away, I want to grab his BC shoulder straps, look him/her right in the eye, and start our ascent. If he/she starts to panic I want to be RIGHT THERE to fix it, or if I have to, recover my spare regulator and leave them behind. If *I* am OOA I want to do the same thing, use my buddy's spare and I want to be nose to nose with him as we ascend.

Is a long hose a good idea in a cave, I have no idea, I don't cave dive, but it sounds like a good idea.