I remember for Suny Buffalo, when I submitted early Aug, they had received about 1/3 of the secondaries they usually do. I'm assuming the same model for other schools
Submit them as early as you can. Spending 2 days vs. 2 weeks turning around secondaries probably won't be what decides your fate at any given school. But if you have the free time to submit them ASAP, do it. If you have less free time, then take a few more days. It's probably only of minor importance.