I read that they can skip till spring if they happen to mature at exactly the wrong time of year--if they were going to lay in fall during a molting season, and then they don't get enough light in winter, they can wait till next spring to lay.
I know exactly how you feel. Some of mine didn't start till 24 weeks, and the only way I could tell who was laying what was because they all lay slightly different colors. I was sure I was the only person on earth who got non-laying chickens, but apparently they will lay really really well once they get started if they hold off till next spring.