Quick question on aluminum and fatigue life...

I know that's absolutely true...aluminum will, at some point, fail with usage. CF also has a fatigue life as I recall. I know the air force learned that the hard way when planes with aluminum wings kept failing. My question is - is it a theoretical problem because the frames are over engineered and the point at which they fail long after we're dead? In other words - how many aluminum frames truly are failing due to fatigue life? How long does it take? My gut reaction is that, while they will fail, the point it happens is so far down the road as to be irrelevant in the real world.