whoa baby! Rocker bolt stretch

If they are torqued properly, the bolts will return to the original dimension assuming they are being loaded within their tolerance. Rocker shft bots (grade 5, 5/16 shaft) are nowehere near capacity at 18 pound feet. They are beyond it at double...lol. You should also check the rocker shaft - if it's factory stock, and you're running a roller rocker, you may have squished it out of round. Thickwall shafts will just pull the threads or break the bolt. But thin shafts can deform.