By not changing your needle at least every 8-10 hrs of sewing or serging, you run the risk of shredding thread, burs, tears on your fabric, a very noisy machine and poor quality of your stitches, just to name a few things. Needles are the cheapest thing to use in sewing yet the most overlooked. You can fix a multitude of problems with sewing by simply changing the needle and using the proper one for the proper fabric. I have taught machine usage for 11 years and work for a dealer. For me, it isn't worth ruining a garment over something that cost less than a dollar.
Roma