They work fairly well. My buddy in Florida uses one in his Cozy MKIV and keeps the re-freezable packs in a mini freezer in his hanger, so they are always available when he wants to use it. The cooler is large though, and takes up a lot of room in the back seat/luggage area and a good deal of weight. He usually only uses it on long XC flights as ATC likes to keep him at low altitude for a couple hundred miles going to and from Michigan. He turns it off when he gets to altitude in cooler temps. He says he gets a couple hours of use before the freeze packs loose their freeze. More than enough to suffice for his trips.