I have a 0, 20, and 40 and the 20 is the most used. I like at least a 10 degree cushion between the quilt spec and expected temperature. I use a sock or UQP to widen the comfort range. The 40 is mostly used during warmer summer days and day hikes. It would be easier to justify a 50 than a 30 because I have the cold side of things ... covered. But even a small breeze can chill on warm day (especially if relaxing after a swim.