W.P.
Dear L G:
Given the price of eggs, I would toss them afterwards, too. But here's a rule of thumb: Put each egg into a large cup of water. If it floats, it's over with. If it stands up on the bottom, it is borderline. If it lays mostly sideways, it's good.
No guarantees, but when eggs rot the gas on one side of the egg expands and makes it come up to the surface.
Regards,
W.