My Bailey quilting machine's bobbin is plastic, and it starts to rattle when it begins to run low on thread. However, I continue quilting until it runs out. I just know then to watch carefully.

I agree! I think any machine that costs as much as the Brother Innov that I now have, should have a warning light or bell or something. It's ridiculous, using computerized machines, that we can still run out of bobbin thread and not know it!

I wind extra bobbins, however, my Pfaff tells me on my screen when it is close to the end.

Mine tells me, but also a little far in advance, so I turn it off but it also makes me aware of how much I have left and I can usually guess about how much more sewing I can do, than I can turn my sensor back on. On my regular computerized or mechanical I usually find out long after I have been sewing that nothings together.

I have a bobbin case, not a drop in. I can't see when the bobbin runs low. However, when I ask myself "I wonder how much bobbin I have left", I am usually down to a few feet. Initution, I guess.

Mine beeps too but I watch after that and push a little more that it says because it seems to be able to do some more seams. Guess I don't do what it is supposed to be. LOL

My machines are all vintage....I can usually tell because the sound changes, and the bobbin case rattles. Don't find it a major headache though.

Mine tells me, but way to soon. I found at first I was throwing away a lot of thread. Now I keep an eye on it after, it has told me, because I know I have quite a bit left to use.

Mine makes a weird sound like a gentle pop and then the fabric I'm sewing bunches up a little when the bobbin actually runs out....it's a straight stitch machine, a vintage 1941 Singer.

My Bernina #730 gives me a message.
Great feature.