I argued that it was wasteful throwing out perfectly good day-old coffee and it's not like it would be spoiled.
Coffee brewed can be
removed promptly from its heat source and kept in a covered container at room temperature until the next morning. It will be fine to drink, just needs to be reheated to your liking. You could even go a second day with it, but its flavor will degrade.
I do this commonly. In fact, whenever I work from home on consecutive days, I brew one 12-cup pot of coffee on, say, Monday morning and drink from it through Tuesday. Sometimes I store it in a carafe on the kitchen counter; sometimes I just leave it in the pot with tin foil sealing the top. Sometimes I'll put the carafe in the fridge to have iced coffee later.
The important thing if you're going to drink coffee this way is to remove it from heat ASAP after brewing. If I'm brewing for a house full of people, this is not necessary -- the coffee pot will be emptied in no time. But if I'm the only one drinking it ... leaving 3/4 of a pot of brewed coffee on the burner for hours on end is a bad idea.
At my house, if there's something like 1/4 of a pot left from the previous morning ... sure, I'll brew more coffee on top of that with fresh grounds. No issue at all to me. Flavor is fine.
If it makes a difference (and it probably does), I don't drink coffee black. Subtle degradations in the the coffee's underlying taste get blitzed by half-and-half and artificial sweeteners.
...
Why yes, I have tried once-cup-at-a-time brewing. Perfect for someone making coffee for one, they say. Well, I tried a proto-Keurig from back when the one-cup brewing machines were a novelty, and the thing leaked water all over the place AND wouldn't actually get any coffee into the cup. I'm sure Keurigs and all are much better now, but I haven't given them a second chance --
give me Joltin's Joe's reliable Mr. Coffee for my morning cup.