A word of warning to my fellow painters... Don't let your paints sit around for an extended period of time. I have quite a few bottles of Vallejo Game Color paints that have gone bad. They have turned gummy, chunky, or somewhere in between. So far it's mostly yellows and oranges that are suffering this fate.
Maybe it would be a good idea to at least give them a good shake every couple of weeks and keep the binder and pigment thoroughly mixed. It might also be advantageous to on occasion add a few drops of distilled water and/or Vallejo thinner.
This is probably a good warning for me to not buy a bottle of paint until I actually need it. Then again, my one (known) local supplier of VGC isn't open at 0300. :)