You've gotta remember that aluminium has no defined fatigue limit which means that if you keep cycling load in an aluminium component, it WILL break at some point.
It might be that it takes a thousand years to break under normal operating conditions but break it would given the chance.
Now rockers take quite a pounding, but if your gran bought an E30 from new and never revved it above 3000rpm, the rockers would last for absolutely years. However, if your old-man-racer grandad bought an E30 new and regularly straffed the limiter, a rocker would likely as not have broken in the last 20 years and quite possibly below the rev limit.
Guess the moral of the storey is that a new set of rockers would be "safe" to a higher rev limit than a 20 year old set.
There, that was boring wasn't it!
)
