If you are registered, you can go in/out of track at any time. If you're not registered (arrive after registration) LRP usually lets you in. The track changes their ways so much, you never know. I have been allowed in with no problem, at others times I had to leave my drivers license and pick up at registration the next morning, and one time they took an entry fee (like NHIS). But one way or the other, you should be able to get into the track Thursday night !