that "new memory load" is functionally zero, since no one would have to remember that. By the time the Extra week actually arrived, people would have been looking forward to it for an entire year, and it would not catch anyone by surprise. No memory required. Even subterranean cave trolls would be aware it is coming.
I think it's a nice idea especially if we could have a big weeklong worldwide party once every 5 or 6 years