Originally Posted by Tink's Mom

Needles should be changed every 8-10 hours of sewing, due to the fact that needle develop a burr on the tip. Think how many times is just one hour that needle has gone in and out of your fabric...a dull needle will punch a larger hole in your fabric, cause tension to be off, and on some fabrics catch on the fabric and cause a pull.
I was trying to get a bit more mileage out of a needle and the burr caught on the diaper that I was making a bit fancy and created a pull all the way across. I now have a fancy dust cloth...