Down loses its loft when stored compressed hard for long periods of time. It is best stored in a large cotton storage sack that allows it to loft completely or stored hung up in a tall closet that is dry. Some loft can be restored by tumbling the down bag in a slightly warm clothes dryer- make sure that there are no sharp edges or snags in the dryer drum.

Designs vary so many bags allow for the down to be shifted to the top or bottom as needed in warmer or colder temperatures. Down under you is mostly useless because it is compressed by body weight. For that reason I use a quilt that has no bottom sheet.

Warmth ratings vary widely and most manufacturers ratings are very optimistic for the average person depending on metabolism, degree of hydration, how tired you are and how much food eaten recently. The usual way to rate bags is by the amount of loft above your body in inches. An average of 2 inches of 800 cubic inch fill down all around you is usually rated at approximately 20F.

A poorly designed footbox can lead to cold feet unless you add heavy socks or down booties.