Double sleeping bags are useful for three reasons: They are less expensive than buying separate sleeping bags. They help you be more warm, with the body heat in  a cozy surrounding. They also make you feel like you are sleeping at home, with your partner by your side. And then tehre is the romance angle.

Tips: Don't put your sleeping bag in a washing machine. DO a spot cleaing. Store your sleeping bag out of its stuff sack. Remember, you as much insulation between your body and the ground as you. So check for insulation ratings. In cold places, always go to sleep wearing woolen caps, warm socks and long johns.

The best double sleeping bag: Big Agnes Dream Island (built-in sleeping-pad sleeve that prevents the bag and pad getting misaligned in the middle of the night.)

The second best double sleeping bag: Sierra Designs Frontcountry Bed Duo (zipper-free design)

The best affordable double sleeping bag: Alps Mountaineering Twin Peak 20°