Originally Posted by
3alarmer
dnomel:
Since you have thrown this open for general comment
and opinion, here is mine. All aluminum alloy frames will
eventually fail, if ridden enough to subject them to
repeated small repetitive impact stresses that lead to
stress fatigue.
The same is true of every other frame material as well since bike frames in normal use will regularly be subjected to stresses beyond the fatigue failure limit. Fortunately that 'eventually' for aluminum as well as other frame materials is usually long past the point where the frame has been discarded for other reasons. So far I have personally only experienced fatigue failures on a couple of my steel frames and still have an aluminum frame that has already far outlived those in mileage.
At least the seat tube crack is in a very visible location so the OP could keep a close eye on it and quickly spot any elongation.