Excellent explanation by Skylar. As a rule I don't notice parallax issues from 50 to 350 yards. I also don't own any scopes higher than 10x though.
Brad, Thank you. You're right, in most cases your typically will not experience any issues within that yardage. It could happen. Although in most cases, it is not necessary.
Thanks for clearing that up Skylar. Sounds like you could be potentially handicapped without the ability to adjust it.
Brad, it greatly depends on the magnification. On higher mag, the reticle is more likely to appear off center if you do not have perfect head position. If you are using low power, then this is a moot point, because it is not something to be worried about. Just remember, that with using that VX-3, that once you cross over 12X it is likely that some parallax will be detected. Then just move the focus in the direction in the way of re-centering the reticle.