Never! Unless I`m at a party and it gets so late that I decide to spend the night there, which hasn´t happened in years. I would feel so dirty going to bed with my makeup on. Especially since I wear long-wearing foundation, it would literally stay on my skin all night! No you do not age faster, nor will you be covered in acne the next day, but it´s still not great for your skin. If I know I won´t be going anywhere later, I´ll remove my makeup right away when I get home, along with putting on sweats....it just feels more comfortable that way, and that way I really can´t be too tired to wash it off later at night.