You can customize them up to the 30 day mark.
After that it takes 24-48hrs to process the order and then GENERALLY 5-7 days for it to arrive to you after that.
So MOST people get them by around 21 days prior to check in day.
You lucky people, us Brits have to wait until we check in until we collect ours. I think if it came in the post I would be wearing it from that moment though
it can be as little as 2 weeks ahead of time if it's a busy time of year. (official website doesn't say 2 weeks but warns busy times of year they will arrive closer)