Maslow's Hierarchy of Needs?
A couple of weeks ago I had a backlog of Extras, but it was because I'm in Texas and we had weirdly cold weather that knocked out power, froze a lot of people's pipes, etc. I came through pretty unscathed, but puzzles became a lesser priority for a few days there. So my 7 day average probably hit zero before I got back in the groove. And then a week later I was back to my usual weekly total with all the extras added in. I bet I'm back to normal by now.
That's a dramatic example, but if I'm short on time, the Extra is the first puzzle I'll skip since it has the longest time period to return to it. Then the 12x12 or Tuesday 9x9. So I might get a bump that way.
I know this isn't rocket surgery. And I realized while writing that you are really asking about purposefully holding puzzles in reserve. I suppose it's just nice to see yourself topping the leader boards. Why let jpoos have all the fun?!