Hi,
My Babylock dealer told us to change our needle every 8 hours of sewing, or at the start of a new project, use your good judgement. But, don't wait until it breaks or bends etc.!
I know with my embroidery I can tell when I need a new needle, my thread starts breaking, change the needle, problem solved.
Needles are cheap, machines and our fabrics are not.....
Bev