I keep hearing things like: If you have titanium chainplates, or, things like the prior comment: If the standing rigging is toggled correctly.... then what? You don't need to tune your rig correctly?
I really think it's more like having oil in an engine.... without it, it is just a matter of time, no matter what kind of engine, or how things are adjusted; you don't want to abuse metal if you want to get the full "life" from those parts.
As far as how much a mast has to "pump" to cause metal fatigue to ruin / break a chainplate, well, from what I understand, you really don't want any pumping at all.
Sure, there will be some flexing from wind changes, but when it gets to the point of having a vibration / pumping action, something is really wrong.