At some point this will happen with plastics too. Soo much plastic is ending up in nature, with soo much energy ready for the taking. When one fungus or bacteria mutates just right to munch on that feast of plastic, that vast energy source will ensure that organism multiplies rapidly.
And that is when plastic stops beeing useful for many of the tasks we humans use it for. If your plastic container decomposes as rapidly as a cardboard box, it will quickly become much less usefull.
You do know that his 40hours a week was a dramatic reduction in working hours compared to the norm at that time?