HK Airlines has an interesting sale where 45 days prior to the date of departure they offer a Super Sale to various destinations. But the sale really isn’t that, it’s valid for a whole bunch of dates, depending on the location. I was looking at Shanghai, there are flights for $450 or $1113 roundtrip in October, which is way past 45 days from today. I think the term should be booking prior to 45 days.
You may just want to check HK Airlines regularly if you are planning a trip to one of their destinations. The sale dates vary and you really just need to see if you spot a cheap fare rather than relying solely on the terms they outline.