StoneNYC, what you present is a valid point but I would say the old-shot photos are not perfect.

I found the roll of film I shot before my half-and-half roll and those were developed at the time. Compared to the 12 years later developed roll you can definitely tell the difference.

Yes, the old-shot photos can look perfectly usable, but there is degradation.

Even 40 year old found film can be processed to return usable results. But those old exposures degrade with every year they go undeveloped. They aren't losing speed they're losing strength.