Matching dye lots (or not) has always been something to be aware of whether it is fabric , knitting yarn, thread, etc. When buying any of these products it is always recommended to buy the amount you will need for a certain project at one time because there can be differences in dye lots. If you underestimate, it can be a problem. If you just like a color and want to use it again for a different project, differing dye lots shouldn't have too much impact.