I talked to LSAC they said we should get emails 3/30 and 4/1

I did mine the day before I took the LSAT. Mine only took four days to get approved. I would recommend you do it before the test, so you get your scores on time.

You should be able to up until the week of the test. Go to your LSAC account and click on View LSAT Registrations & Statuses. From there you can change the date of your test.