Blew $60 on a fleece liner for the Colorado Trail and it paid me back
Honestly I almost left it at home because 14 extra ounces felt dumb, but it got down to 28 degrees on the Collegiate West stretch in June and I slept fine while the guy next to me shivered in just his quilt. Now I pack it on every trip above 9,000 feet. What's your weight cutoff for bringing a liner?