I’ve been known to come in Monday morning, realize there is un-drunk coffee in my cup, and drink it. It’s often a little strong due to evaporation - almost strong enough to start making that the default process.
I’ve never heard of cleaning coffee apparatus. I’d be surprised if anything besides humans can survive my coffee.
It eats through the equipment every 3 years or so.
When I had a conventional coffee maker, I mostly just rinsed it out and the coffee was always excellent; then Mr Coffee hit the scene, followed by clones, and I used them, but didn’t like them because no matter how little I made, it seemed I was always throwing out more than I drank. So that’s when I got the Keurig.
And since I only drink coffee once or twice a week, it’s good. The K-cups are sealed so the coffee doesn’t go stale.