[QUOTE=A.R. Cane]
The responses are interesting to me. This was a common practice during WWII and my parents certainly did it. Coffee was rationed and expensive when available. Surely there are some other older Dopers who remember this?
[/QUOTE]
I don’t remember it, but the fact that coffee was rationed and expensive surely had a lot to do with the practice; it mostly wasn’t done by choice.
Nowadays, coffee is cheap, so we don’t have to make hard choices like that.
I’ll make mine fresh each time, thanks.
This is a pretty common ‘tightwad’ tip – I’ve seen it in a lot of books on frugality. I don’t do it myself, except in extremity (I need a second pot and am running out of coffee). Usually, though, I use a fresh filter and fresh coffee for each pot.
That said, I do use gonzomax’s grandmother’s method for reusing teabags.
[QUOTE=Spectre of Pithecanthropus]
…In the beginning of my IT career I worked on VMS machines and thought it would be great if the coffeepot could somehow be wired to the cluster so one could do a
show dev dev$coffee
to see how full it was, and know when to go for your next cup.
[/QUOTE]
You’re aware, I’m sure, that the very first webcam was for just this purpose?
[QUOTE=Queen Tonya]
Then why not just use half the measure of water and fresh coffee and not re-use anything?
[/QUOTE]
OK, I’m late coming back, to get my smacks for not treating Coffee as the holy beverage it seems to be to some. I guess I like my like my coffee strong, oily and bitter. 
Them once used grounds got some caffeine and coffee goodness left in em.
Y’all are wastrels, sez I.
[QUOTE=ParentalAdvisory]
So you would be okay with your favorite fried food being fried with yesterdays oil, mixed with a little bit of todays new oil?
Count me in for gross on this subject…
[/QUOTE]
Actually, that’s the way you’re meant to do it. Foods fried in fresh oil come out pale and underbrowned. New oil needs a bit of old oil mixed into it for proper browning.
[QUOTE=The Sonoran Lizard King]
OK, I’m late coming back, to get my smacks for not treating Coffee as the holy beverage it seems to be to some. I guess I like my like my coffee strong, oily and bitter.
Them once used grounds got some caffeine and coffee goodness left in em.
Y’all are wastrels, sez I.
[/QUOTE]
Once you get a good whiff of fermented coffee, or moldy grounds, you’ll be averse to repeating the experience, sez I. 