Generally it is best to turn in the secondary at least within two weeks after you received it. If the school gives you a submission deadline, try to submit at least two or three days before that deadline. You can imagine that it is extremely difficult and time-consuming to fill out each secondary application. Balance your time and figure out your priorities. Even though you would like to put forth your best effort for each application, focus more on the schools you really would like to go to. Submitting sooner is good but you do not want to rush this process. Do not sacrifice quality for the sake of turning in your application quickly.