OK, I went to search for my usual keywords, and I dropped again, like I had at the beginning of this month, and when I looked further, it seems all cached pages are back to august 3rd, as are the results associated with them. Anyone else experiencing this?
Newly updated pages seem to be bodged into the index. The cache typically sticks for around 5 days and reverts back. Changes may not stick until a full update occurs every few weeks. This used to be called the Dance but since algo changes, backlink updates and index updates all seem to occur independantly, index updates may go unnoticed. It may also be the case that partial updates of the index occur daily but the whole rolling process still requires several weeks to complete. If this is happening, then I guess changes will stick after one cycle completes.
That, at least, is my experience but I haven't bothered to observe this behaviour for a while.
I can see no pattern to this and am not sure (IMHO) that it means anything. I have a number of pages that have been cached from every day during August and some are above where they started out in SERPS on 8/3 and some below. To me it just looks like a normal pattern/flux of SERP changes.
Our Google traffic collapsed on August 3-4. Somewhat recovered on the 12th. Have completely recovered to pre August 4 levels as of today. Not sure if it's that the index is from August 3, or the algo has switched back to what it was August 3.