I find I work best in two sprints less than 6 hours, I totally get that long sprints reach a point of diminishing returns. My question is Why is six hours so mu

I find I work best in two sprints less than 6 hours, I totally get that long sprints reach a point of diminishing returns. My question is Why is six hours so much better than abandoning shift-based timing for something like task-based timing instead and cutting out all that extra time, not just reduce it.