For PHD program, few schools review your application before the deadline. Generally, BS gives applicants about 2 weeks leeway to mail transcripts and recommendation after the deadling but you should submit your application before deadline. Generally, top 20 begins to review applications in Feb.; top 50 review applications in mid of March; others make decision before April 15. Even BS review your application material, no decision will be made before deadline. But it is a good idea to talk to coordinator or prof. in person as early as possible.