Each night when you lie to down to sleep, there's a dynamic fluid change in your spine as the discs become parallel to the forces of gravity. By stretching and decompressing before bed, you "open" the door to the disc so it can imbibe fluid. Much like a garden hose will straigthen when you turn on the water, so will your spine lengthen and potentially straighten while you sleep as the fluid enters. Don't blow this great opportunity to keep healthy discs and joints. Stretch before you fall asleep.