The parking lots at WDW never close. That being said, don't leave your car parked there overnight it might be towed. If you arrive at the lot early enough (more than 2hrs before opening), the booths may be unstaffed and signs will tell you to proceed to the lot and you will get "free" parking. Its completely OK and your reward for getting there super early. Chances are if you are there more than 90 minutes before park opening security will be a breeze and take only 1-2 minutes. If you are only there 30 minutes before opening, security checks might take closer to 20 minutes. To be safe, try to pull up to the parking lot no later than 45minutes before opening. That should give you plenty of cushion to get in before boarding groups begin booking.