At least the Kelty Cosmic Down is EN13537 tested, so there are some relatively objective criteria for its temperature ratings. With most inexpensive sleeping bags, assume that the minimum temperature ratings dreamed up by their marketing departments are 15*F or more too low!

The Cosmic Down probably won't last as long as a high quality down bag, and is, of course, heavier. However, it should outlast most synthetic bags if well cared for. (Synthetic insulation doesn't recover nearly as well from being compressed.)

More on EN13537 ratings here.

Edited by OregonMouse (01/08/15 07:04 PM)
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey