The “comfort, “limit,” and “risk” ratings are definitely being exploited by the marketing folks. I was just looking at Thermarest bags and quilts; a couple of years ago, they named their bags on the comfort rating, but now they use the limit rating (the “Super Sun 40” of a couple years ago is now the “Super Sun 30.”)

While I was shopping for the quilt I wanted, I ignored the number in the name, and purchase based on comfort rating. That way, I’ve got a margin of error built in: if I buy a bag with a 40-degree comfort rating and a 30-degree limit rating, I should be good if the temps unexpectedly drop into the mid or lower 30s. (FWIW, I ended up with the Thermarest Vesper 32 - it has a 41 degree comfort rating, and I’m at the point in my life where I cancel trips if the lows are predicted below 40 - which is an in-town prediction; it will probably be 5-10 degrees colder in the woods. The other safety margin is Montbell Superior Down jacket and matching down pants, which I can wear in addition to the longjohns. I sleep a bit cold, so I wouldn’t use any pad rated lower than R-5.)

Marketers do the same thing with packs, but there’s no standard method: the “Maxout 60” has a 60-liter capacity by counting the lid, outside stuff-it and water bottle pockets, and main compartment; the “Bonecrusher 50” counts only the main compartment. Arrrgh!

In the end, it’s not enough to go by the temperature ratings. You have to know whether you sleep hot or cold, whether you’ll be using it in the open or in a tent (tarps and three-sided shelters provide only minimal windbreaks), and what type of trips you like to take.