So is there any merit to letting your skin "breathe"? I try to go one day a week with no makeup for that reason, but it might just be hooey.
So long as you are using products that don't normally irritate your skin, I think the only issues are using bacteria-laden cosmetics or failing to wash your makeup off at the end of the day. Whatever you do during the day, presumably you spend at least 8 hours out of every 24-hour cycle makeup-free. YMMV if you have particularly sensitive skin.