9 hours started doing that (9pm6am) when I was in my early 30's, still doing it decades later. Habit now. For those who have shoulder/hip pain when side sleeping, mine vanished when I switched from a traditional mattress (extra firm) to memory foam (still extra firm). If you're a bigger person, like broad shoulders type, then getting a thicker pillow will alleviate a lot of neck pains too. Back sleeping is supposed to be better, I can't do it though.