I don't have any idea how many colors of X2I have, but some I've had since before Do It was ever mentioned at CCM. They are thick and yes they will settle but it takes a long time for them to settle much. I put the nuts in every color I get, X2 or otherwise and I take time every couple weeks to get them all out and give them a rattle. If you don't want to play with the stainless stuff and have a little time on your hands should a color hard pack, you can scrape it around in the bottle using a long screwdriver. If it hard packs, pour the liquid into another bottle so you minimize a mess, add about 1/2" of softener, worm oil, or stabilizer to the colorant bottle and scratch away with the screwdriver bit until you have as much of the packed stuff mixed into whatever you've added as you can without poking a hole in the bottom. Then add your stainless nuts and pour the colorant back in the original bottle and shake away to blend everything back to a useable state.
As I have used the thicker colors and the levels in those bottles goes down I have added some stabilizer and/or softener to the contents to help loosen the remainder up. I agree that the stuff is thicker than thick, but I also feel that taking time to keep these product agitated is important especially if you are going to follow color recipes and hope to stay constant.