I do see your point that they are usually for cruises coming up within the next few months. That is when the cruise line figure out that a ship needs to be sold so they drop prices.
Especially right after "full payment is due" date after some people cancel out.
In my articles I always say that "being flexible" is the key to finding good bargains.
1. Be date flexible, the same cruise four weeks apart can be discounted by over 50%.
2. Go where the market demands. Most people decide where they want to cruise that year instead of doing research to see where the bargains are. If you followed the bargains you would most likely go to all the same places, just not the same years. This year the Med is very softy, but Alaska is pricier - three years ago Alaska cruises were as low as $299.
3. I don't really agree anymore that sales are just for "lead in" prices for lower category cabins. These days, like on the Solstice class ships, the vast, vast majority of cabins are balcony, so the lower categories cost barely less because they sell out much faster.