Oh dear. I wish I could answer this more anonymously. I am notorious among my friends and family for drinking old coffee left in the mug in the center console of the car, often for a week or more.
Coffee is safe to drink , as far as I ma concerned, as long as there are no fuzzy things growing on it .Today is Wednesday. At present I am drinking a mug of room temperature coffee from a pot I made Monday afternoon.
I make my coffee medium strength. It tastes acidic although I have never run a pH test on it. I use Chock Full O'Nuts brand when I can find it. I don't use any additive, flavors or sweeteners. I like it cold and black, just like Dick Cheney's first heart.
Nothing bad has happened to me that I can attribute to old coffee; I have been doing this for perhaps 40 years since college. It was a habit I developed when I was very broke and never lost.
Don't hate me.