A few days ago, I did a test booking for LHR-HKG-LHR and both direct flights showed only Business Flex/Essential pricing. Via MAN, etc I could still see Light.
I went all the way through to seat selection, and I think only the bassinet seats were unavailable, so I was surprised Light was no longer available.
Going back in today, I can now see Light again in both direct flights. So I'm confused. What drives whether or not Light is shown, and why would it "come back"?

If I want to take advantage of the lower pricing, do I just need to book as early as possible? I'm wary of booking flights too early as I've found a lot of airlines change their timings quite often between now and d-day.