We uploaded our first Disavow list (over 1500 domains) in February 2013 (6 months ago). We submitted a reconsideration request (because there WAS a manual penalty that I knew about). Manual penalty revoked one week later, in early March. Until last week, all of those backlinks still showed on a link: search. Now, most of those links are gone, but a handful remain. When I log in to GWT, ALL of the links still appear. So, it took 6 months to see a reduction in links showing for the link: operator and still no reduction (actually an increase) in GWT. No change in rankings whatsoever. We get MAYBE 15 visitors a day from Google. So, if you eventually see beneficial ranking changes, it could take many, many months. We've even had a Penguin refresh since my disavow list was first submitted. Nothing came of it.
Our site has been bombarded with spammy links over the past two years (presumably negative SEO since I am in a very competitive niche), and the influx of backlinks from those (and new) sources continues. I have to routinely update the disavow list to add new domains. For instance, in the past two weeks, a new domain is pointing 2,000 spammy links to our site. It's a sad state of affairs to say the least. Long story short, you will be waiting a very long time.