I finished my first bottle of black in weeks, my second bottle lasted for years

I was sitting next to the painting station helping with some work on my PC, as I was just waiting around I looked across to my pots of paints i decided to add some water to them and gave them a good shake.

These are the first bunch of paints I got for this hobby, all except the black. I was told that the easiest way to prime a mini was to paint it black. I did that as it made sense with my Chaos armored units. Later on I learned that black is actually the hardest color to paint and paint over I stayed away from this pot for a long time. Not until recently I had enough skill and courage to use black paint, but still I haven't gone through my second pot.