What should I do about my parents life?

Sounds like your parents have found the wonderous drug of VIAGRA! They are obviously having fun, but it is making you uncomfortable and you need to let them know. A face to face encouter might be too uncomfortable, so try leaving a respectfully written note explaining that you know they have needs and it's natural and you understand that they have physical needs, however dirty sheets in the hallway, trashed bathrooms and hearing them at night makes you feel uncomfortable.