Many years ago I worked at a smallish office for a company. It was a Monday morning, and I was the second one in. My co-worker was already face-down in paperwork.
I staggered into the break room and saw a pot of coffee there. It was maybe half-full or so. I poured, added the usual stuff, and took a sip.
I almost spat it.
I asked my co-worker whether he thought anything odd about the morning coffee he'd made. He said "What coffee? I didn't make any coffee this morning."
*ponder*
I had had coffee which had sat there all weekend long.
Granted, it was the right temperature. It just tasted all kinds of wrong.