I am just going to add some details to HERO Shor's comment.
Nowadays, the GRE General score has an important impact on either bare admission or the financial support.
The famous schools often use it to distinguish better applicants among the their crowded pool. Furthermore, moderate universities consider it as a measuring criterion to dedicate their financial support.
All in all, the limited universities do not need this score as a mandatory material for the application, but the majority of the universities expect the applicant to provide his/her mark within the application. Actually, sending the scores right after the deadline might be acceptable for some schools. This possibility should which be investigated, case by case, by communication with the corresponding graduate admission department. So, you better check the target programs and if they commit the late scores, stick to the preparation for the test.