Robert_Charlton - 9:05 pm on Jan 10, 2013 (gmt 0)
Here's the thread with an extended quote from John Mueller about recovery time...
Partial recovery from Penguin
To paraphrase what he says... using the disavow tool adds something similar to nofollow to the links you've disavowed, so if you chose applicable links, disavowal will be effective. He adds, though, that "you should... keep in mind that it takes quite a bit of time for this to update". Google needs to recrawl those links and also to "update the Penguin algorithm data".
As TMS suggests, this combination of recrawling the pages and updating the data indicates that we'll see abrupt changes, widely spaced in time.