WarBot is correct on that every little bit helps. In the beginning I was submitting to about 70 then I cut it down to top 20 traffic wise while I was working on other stuff. The reality of it all is that sales did drop a bit. Sometimes you just never know where that sale is going to come from. It may just be coming from the list that sends 10 hits versus 1000. Plus how long does it actually take to mirror the site and submit.
I also agree with neticule that if you cannot submit to everyone ya want today then submit to who ya can and the others tomorrow that is if you are not building/submitting everyday in which case I say take a day off
