Hair: if you typically take your bath in the evening and don’t completely dry your hair the moisture in your hair can shorten the life of your pillow. Not completely drying your hair before you go to sleep will significantly impact the life of your pillow and cause your pillow to yellow prematurely. Your pillow will go flat and lose its resilience the more your pillow is exposed to moisture from your hair.
Perspiration: There are many reasons why you weightless in the morning than you do in the evening and it's not because your body has had a chance to digest dinner from last night. One of those reasons is that you perspire while you sleep. The average person can lose as much as 1 liter of water overnight and that 'water' has to go somewhere and it's usually into your down comforter, feather bed or pillows or combination. Do NOT underestimate the impact a duvet cover and your flat sheet can and will have on the amount of additional, and potentially unwanted warmth, they can add to your bedding environment.