They have separate ballots for each group of potential attendees, starting with people who’ve been 5 times or more, then 4+ a week or two later, and so on down the line.
The ballots for the more seasoned attendees have fewer people in them, so your odds of getting a ticket are higher. In addition, if you miss out, you can apply in later rounds as well. So in theory you could lose out in all the rounds and end up without a ticket, but you’d have to be insanely unlucky for that to happen: in practice once you’ve been a few times your odds of going again are pretty much guaranteed.