I live in an apartment with 1 girl and her boyfriend, another guy and one other guy just left. When we moved in all the girl's friends thought she'd be miserable with 4 dirty MEN in the house, but her response was always that we're the most 'domestic' men she knows. We keep things clean for the most part, especially the kitchen, we vacuum all the time and clean the bathrooms.
Now my room is another story. I tend to have an 'organized chaos' thing going on. I usually know WHERE I tossed something at random, I just remember having thrown it there when I need it. So my room tends to LOOK like it's completely disordered and nasty, but it's really pretty clean. I do tend to pile up empty glasses and soda cans, but not tossed on the floor or anything.
When it reaches the point that I CAN'T remember where I tossed something or I can't find it at all, then I know it's time to clean.