Christmas is only a peak time for personal travel. It's actually a slow time for business travel. And for this reason, it's a lot easier to find award seats in business/first class at Christmastime than in coach (at least domestically). But of course, most families (or even most individuals) don't consider paying double (or more?) of the miles just to get a seat up front, when all they wanted was to travel cheaply for their Christmas trip. So I've found (on the routes that I've looked at) that those business class awards can persist for a while, on Christmastime routes that pretty much never had coach awards available. That does seem 'effective' for the airline.

Similarly, many domestic airlines have an "anytime" award for "just" double to triple the miles available on most any of their own flights until it's sold out, but again most families (and most individuals) ignore that because it goes against their idea of "value" (and/or because they haven't accumulated enough miles to "afford" those). The airlines play with the award cost of "anytime" awards to make sure they don't substitute much for paid travel, so that does seem "effective" for them.