Originally Posted by
BigAura
"But note that vapor barriers should only be used when it's really cold - below the normal comfort range of your bag/pad combination."
That was my point: when you're freezing use it. Personally I'd rather not get to the point where my pores shutdown. I'd say --> not a good plan, for a winter tour.
Sure if you always know exactly how cold it's going to get you could carry the weight of a bag/pad combination to handle it. But a vapor barrier liner only weighs a few ounces and can greatly extend the usable temperature range of your bag. Very useful when conditions change from those expected. And I've always slept very comfortably when inside my vapor barrier so I certainly plan to continue to bring it along on all tours & backpacks where it might get cold.