One of my sites I notice jumps back and forth from a current index update to an older one. Back and forth. The site has 40 pages and the Google cache, when current, reflects that. But when it reverts to an older index the cache says 29 pages (like right now). And when its reverting to the older index my traffic drops considerably. Particularly because in the old index many of my pages were supplemental. It's done this 3 or 4 times in the last few months. Frustrating.