Yesterday afternoon I was at 700 HITs submitted when I started back (after Thanksgiving) around 2:45 pm. Hit 3,800 submissions at around 6 I think?
Probably between 600 to 800 an hour if I had to guess. Depends on how many are up. If they keep going down it takes longer since I have to refresh the page. With individual hits themselves, it doesn't take long with scripts to look at a pair of images and determine if they're similar or not (most usually are...I still do a quick check.) Spiced things up with a few different HITs this morning so I'm actually a dollar up on my last few days if I manage to top out again. If I do top out today and tomorrow, that will be 20,000 HITs submitted for the week, probably about 5,000 shy of the actual limit.