I know I have run out of thread when I take the fabric out of the machine and the seams fall apart. It is infuriating, but I forget to check the (transparent) bobbin. When I do realise the bobbin is looking a bit low I almost will the last run of thread to keep going to the end of the seam. I also talk to the machine and threaten it. DH looks at me and shakes his head sadly. The one thing missing on my Janome 4900 is an independent bobbin winder. I really ought to invest in a sidewinder.