When serving or keeping coffee you should never leave coffee on the warmer (coffee maker) more than 20 minutes! You know what scalded coffee tastes like. It’s really bitter and bites you with a nasty twang.
If you can not finish the fresh pot within 20 minutes ( and I can! ), you need to put it in a carafe or thermos to keep it warm. Most quality coffees do taste better as they cool. If you need to warm you coffee, try warming a cup with hot water first and pouring the coffee back into it. If that does not satisfy you, you may want to add a tad… just a touch, now, of hot water or you could place it in the microwave for no more than 15 seconds. Careful though, micro waved coffee takes on an unforgettable taste that only a zapped cup of java can have.