James,
Your question is a valid one. I can only answer for myself. I shoot routinely out past 30 yards and haven't noticed any problems. Out to that distance my brain does the math for me so to speak, so I just pick a spot, draw to anchor, and shoot. I find that if you feed good data into your brain through consistent, repeatable practice, the little computer on your shoulders will typically put out good data in the form of proper shot placement. I have shot much lighter shafts in the past, and still wouldn't hesitate to shoot 8 or 9 grains per inch on most North American sized critters. Since moving up to heavier shafts (and sometimes bigger critters), though, I have experienced better penetration and really don't notice a great deal of difference in the distance I can effectively shoot. Though my longest trad kill was a whitetail doe at 48 yards, I don't routinely loose arrows on critters out past 30 or so yards. On the other hand, I don't judge yardage, nor do I rely on it to dictate my shot.