I have to admit, I have a bad habit of falling asleep with my makeup on. When I do, the next morning my face feels greasy and disgusting and looks bad too. I think it's always best to wash your face before bedtime.
If you are lazy invest in those 3 in 1 clothes. They remove makeup, cleans your skin and tone. I really like j&j 3 in 1's. Biore' also has some really good ones. Don't ever sleep with makeup on, you will break out.