When the bobbin is empty are you supposed to start over?

[Alpha O]

But the beeping can get pretty annoying, especially when you realize there's still quite a bit of thread left and you just want to finish that line.....

Pfaff 2170 just flashes light. Light doesn't flash if you don't clean out the bobbin area. Lint covers the sensor. 2170 is vertical bobbin, not drop-in.