I somethimes go through 2 or 3 depending on what I am doing. Some days I feel I do more unsewing than sewing and may only use one or less bobbins. I find my Brother also does not completely fill the bobbin. Need to check to see if there is an adjustment they can make to fill it more. I usualy fill 4 or 5 bobbins of the same color if I am working on a big project. So I have a lot of bobbins on hand so I can fill several with the same colors at once.