You could consider placing a few magnets(2-3 etc) at the base of the oil pan(very strong magnets that you know won't come off if you hit a pothole), and drive around for a 50-100 miles before your next oil change. If it's a huge concern, you could always drain early on this interval and see if any other 'metal flakes' come out? Simply getting a UOA wouldn't be a bad idea, but I'd try to catch it from your drain plug mid-stream while draining the used oil to be sampled. Oh, if you go with the magnet idea, just before draining the oil(literally), remove the magnets so any metals naturally rinse out if possible.