It can't be good having any sort of a crack in an area like that.

It's true that those cracks can take a very long time to propagate, but the rate is extremely dependent on the loading. Stronger riders have broken many of them, and I've seen Record cranks where the cracks came in from the webs on both sides, to quite a depth.
The other failures, up along the load path to the pedal eyes, more common and faster growth of the cracks, since the stress is higher.
But the spider-crotch cracks seem to stress-relieve to a degree as the crack penetrates the thicker section, but cracks don't sleep as they say.

Whenever I hear of a bike part failure, I usually first wonder how big and strong that the rider was.