If you ask 10 of your sewing friends when they change their sewing machine needle, you’ll most likely get 5 different answers. The 'every project' designation is quite vague, because some quilts take much longer to piece and quilt than others. If new needles were required for every new garment that was sewn, clothing costs would increase due to the increased needle expense. Because of the varying amount of time it takes for the many quilts I make, I personally don't follow the 'use a new needle with every quilt.' mantra.
With Superior's Titanium-coated needles, you will hear a different sound when sewing (a soft, constant 'thud, thud, thud') when the needle is getting dull. This is because the thin layer of titanium-nitride coating is wearing off. Every time the needle penetrates fabric, there is a microscopic amount of wear on a needle, no matter what it is coated with (nickel, chrome, or titanium).
There are many other cues of a dulling or dull needle that are more recognizable, such as skipped stitches, the top thread shredding, and/or puckering while stitching. If your thread starts to behave strangely and you are experiencing these types of problems whereas you weren't before, chances are that your needle should be replaced.