Sorry to bring you down to these levels 
However I often make a teapot of herbal tea in the evening, perhaps topping it up once or twice.
I have been known, on days like today, to go downstairs first thing and top it up with hot water again. Then drink it. I had someone say to me today in horrified tones that it might be floating in bacteria, which I've never considered. So AIBU? Or are they being sensitive?