The CJO states it's good for 12 months. I was told by HR when I got it to expect a early 2020 class. I received an email for a Dec 3&10 class. Unable to make those I asked if I could still defer to the January invite list and they said no problem. They send out an email with a link to class dates much like the interview email. My understanding is you don't have to pick the first available however once you sign up for one that's where it harder to change to a later date.