My wife (who is very new to backpacking) and I (been backpacking since my teens) have started to go on some weekend trips together. Wifie HATES the idea of a mummy bag and will not even entertain the thought of one. I got us a pair of North face Allegheny 40 degree bags. They are rectangular and very comfortable. North Face also makes a Dolomite version that is claimed to be a 20 degree bag.
My question is are we better off staying in our separate bags or would zipping them together add warmth. I would like to pick up a pair of the Dolomite 20 degree bags for slightly colder weather. I figure we could either us both 40 degree bags or both 20 degree bags and even sometimes one of each.