When In a Relationship Do You Start Leaving the Bathroom Door Open?

When in a relationship do you start to leave the bathroom door open - after the first sleepover? First sex? First anal sex? After you've met the parents? Never? And yes, we know it depends on what's happening in said bathroom… feel free to make a distinction in your answers! (By the way, it turns out that readers of EMandLO.com require UTMOST privacy when it comes to tooth-brushing. Who knew?!)