I have a Nikko Stirling scope (by no means a high end brand) mounted on a 375 H&H magnum rifle thats been Magna-ported as my main moose hunting rifle. Before the hunt, I take the rifle up to sight it in. It has never been more the one or two clicks out in the 12 years it's been on the rifle, no matter how many shots I put through it.
I also know a couple of guys, one with a 308 target rifle with a muzzle break on it, that he fires a LOT, and none of them have ever experienced any scope problems.
I suspect this is just another of those gun shooters myths that you hear about from time to time.