I don't know - I think the length of a ride can be important for an immersive Disney experience. Think of the best, most immersive Disney experiences - they usually are quite lengthy. I remember the first time I rode Splash Mountain (many years ago), when I was five minutes into the adventure (already longer than any other flume ride I'd ever taken), and realizing I was nowhere near the end of a truly phenomenal adventure.
Two years ago, my 60-year-old parents went on Splash Moutain for the first time ever, and I remember them also commenting, about halfway through, that it was the "best attraction they'd ever experienced." And we hadn't even gotten CLOSE to the big drop yet!
I'm kind of hoping that Everest also immerses you in the experience for a while, as well, so a 2-3 minute ride would be a disappointment... Granted, immersion can successfully be done in the queuing area as well (as in, say, Star Tours).