Update from ssanke: The key to making the finish on your spray-painted hardware durable is to sand/rough up every surface before spraying with Rustoleum Oil Rubbed Bronze. (Best I've found for updating hardware.) Also, it's best to do several LIGHT coats or you will get drips. Let dry COMPLETELY before re-installing. I replaced many of my standard knobs with "the real deal" but I did this for larger, more costly handlesets. It's holding up great on our back door which gets *heavy* use.
LiveLoveDIY: How To Update Old Brass Doorknobs With Spray Paint