If for some reason, I had to choose only a couple of juices and give away everything else I own, I have two I could probably get by on indefinitely - Redbeard's Cherry Bomb from Pirate Vapor (black cherry & citrus), and MBV's Cinnamon Roll.
However, I greatly prefer the freedom to vape 18 different flavors during the course of the day if that's what I want to do.
There's also the upside of knowing that I'll never be in a bad way if my favorite juice were to change or be discontinued.
For me, the idea of the ADV is over-rated. I'd rather find a dozen or so flavors with lasting appeal - things that I enjoy today, and will still enjoy 6 months from now.
That said, my fiance is pretty settled on four flavors* - of course, from three different vendors - and would probably be satisfied with any one of the four as his only juice.
However, now I have guilt every time *I* want to try new stuff. "Oh look honey, I got juice again. No, I didn't get you any because you never vape anything but the flavors you already have for more than 5 minutes before you forget about it."
(seriously, he's gotta have 15 bottles of juice he tried once, and hasn't gone back to, not because he didn't LIKE them, but just because he didn't like them MORE than what he already has)
*His top four? Black Ice and Zinger from MBV. Peanut Butter Cookie from Parkes. Mint T Green from New England Vapor Supplies.