I had an interesting experience today. As you might know, I went to a hardware store many months ago and got a litre of paint for each of the colors I was going to use on my Eldar table. One of those colors was Graveyard Earth. I actually ran out of GW Graveyeard Earth and had to finish off some bases, so I decided to skim some off of the 1 litre can.
It worked great. The paint was the perfect color, and while it didn't work feel the same as Graveyard Earth from GW, it easily did the trick for me. Looks great, applied nicely, the whole thing. It makes me consider whether I should get a few litre cans of the paints I use most and just replenish my supply when I need it instead of buying a new pot every single time (which I don't do very often anyhow).
Another thing I learned was that a GW paint pot only holds three tablespoons of paint. That seems like a rather small amount.