My friend is able to get thousands of pounds of beans shipped to him from the Honduras from a family farm. He's had nearly 100 pounds of these beans for over 4 months, he's insisted on selling them. My contention has been that these beans are not fresh and will reduce the quality of coffee that is being sold from them. Is there a typical shelf life for beans to guarantee freshness after roasting?
I think it is generally regarded that beans are still 'fresh' within one month of roasting where the flavour profile of the bean will change over that one month. Dissecting it further, people tend to agree that beans should be at their peak within 2 weeks of roasting. Past a month the bean should show noticeable signs of decline in the flavour profile, losing most of the brighter notes and acidity and providing a much flatter flavour profile as most complex compounds in the coffee would have disintegrated.
You mention that your friend has had those beans for over 4 months, even if measured since the roast date, you can safely say that those beans are stale. At this point there's really no difference between getting rid of them now or later as they should not degrade much further if at all.