Also, the only time I have witnessed actual “sweat out the down” action was in the mid 40s, on a stupid-short trip when I took an experienced newbie (“I haven’t backpacked in three decades but I absolutely positively want to go on that 50 mile trip with you”) out with me. He used one of my quilts, brought with him a beastly heavy three layer jacket and slept with that on, with the quilt over him, and chanted that he was “freezing to death” for most of the night. Later he confessed that he went to a doctor and found out he had an infection (staph, I think) on his skin, and also he was a poorly maintained diabetic. But the down in my quilt was soaked down to clumps in two baffles.
I have at times over the years felt damp while dry inside the tent and it is my impression, unscientific and skewed to subjective as it is, that how I feel is not always true. There have been times that I felt tingling on my skin that I thought was silnylon misting – it proved to be untrue, just humidity increasing in a light shower and the inside of the tent was cold but not wet. Cold nylon can feel to me to be wet, and there may be a little moisture, but I’ve not observed significant degradation of loft in such conditions. I wonder at times if when I perceive cold if my body responds by upping the circulation. I have had sweaty skin above freezing despite it being 39-45F and not really all that warm, by our day to day civilized standards. Nor did I perceive that I was warm — until I sat up out of the quilt and got back in it.
If I were routinely out below 25F I would consider an overbag, but have not had too many issues as I am, with the quilts I have.

