It is not often you get the exact number of drills for your Diamond Painting. You usually get a bunch of diamonds left over when you finish it. The question is what you can do with the left over drills? You can save them and use them for other projects if you mark them the right way.
Since the drill manufacturers make use of DMC-numbers, one can actually mix the drills with each other. What you have to keep in mind is that the shades may differ slightly between different suppliers. So before mixing together all the drills of one color, you should check that the shades are the same. If they are not, then do not mix them, mark them instead with the DMC-number and note that you have several shades of the same number. If you want to read more about DMC-numbers, you can do this here: DMC-numbers – what is that?.
By saving the drills you have over you can use them for other paintings. If you lack any color in an ongoing project then you can look if you might have got drills from a previous project of that color. Check that the shades are a match and if they are, you can go ahead and use them and you do not have to wait to get more drills.
If you don’t know the DMC numbers of your drills, you can always save them anyway and use them to decorate something. There are those who used leftover drills to decorate candles, Christmas cards and the like. I have even seen one that decorated a pair of high-heeled shoes. Only your imagination sets the limits for what you can do with the left over drills.