You know, that reminds me of co-workers on Guam. They all drank coffee. At the end of the day they would leave their coffee cups, with just a little bit of coffee in them, on their desks. The next day when they came into the office they never cleaned their cups from the previous day. They just left the crud from the previous day in their cups and poured in fresh coffee. They said the old grounds "gave it an extra boost."
I know! I was completely bogued out when it dawned on me that people LIKED that!
Now, I don’t clean anyone’s coffee cup, no matter how nasty!