After making my coffee in the morning, I always put my leftover coffee in a thermos because my coffee maker automatically shuts off after a certain amount of time and it gets cold. I cook for one so I don't want to waste it by throwing it out. This method is good for any hot liquid, tea, hot chocolate, etc. if you want to make it at a convenient time and have it ready for when you need it.
This is also great for camping when you only cook once or twice a day. You can also put leftover soup, etc. in a wide mouth thermos.
And if you have any left over after you've had your fill, pour it into a pitcher you keep in the fridge, keep topping it off everyday and you're ready to make iced coffee anytime!