I agree with Sparks1093 completely.
I would say this. If you are a budget traveler and you are ONLY concerned about being on the ship and you really don't care about what cabin you are going to get, waiting to book later will save you 10-20% on the cruise fare (but nothing else).
If you do not like having very limited choices or you have some particular needs, book well in advance.
The whole cruise marketing machine is there to make it seem that every cruise these days is sailing completely full and if you don't make a deposit tomorrow, you will be standing on the dock. My January 2024 cruise was booked in December 2022. Had I booked the same cruise last month, I would have saved about $300
I have found that the real deals are during shoulder periods when families cannot travel. I have found great bargains on older ships as opposed to the "latest and greatest" and the like.