I use as many projects as can get done in the time I need. So lets say I run 350 connections on a given machine, which is accurate. Then lets say I want to cap the project at 100,000 submissions for a day. So lets say my machine can work thru 1,000,000 submissions in a day. Then I would run max 10 projects at once, and I stagger the start time thru the day as well, when it makes sense. I just kind of made up some round numbers, but my machines can typically get in around a million submissions a day, give or take. So just figure the total submissions and then divide that by the max you want to submit per project and thats how many projects you "can" run. now how many you need to run, that all depends on all sorts of stuff.