My Bernina 750QE has been really good so far, it has giant bobbins compared with my old Janome, and it takes a lot of stitching before they run out. When I was quilting Flower Garden I would check the bobbin first thing in the morning before I started quilting, the bobbin would usually last 2 days of quilting before I needed to change it over.
These photos show how much larger the new Bernina bobbin is,
the top bobbin in both photos is the Janome bobbin.
There is also a screen where you can check how many stitches you have sewn, I suppose you could note down the amount of stitches different projects took, if you were so inclined - I'm not :)