I'm not sure I agree completely with the 6 month guideline and losing CQ points. It comes down to individual bean character, how it is stored, etc.
I'm certainly not saying 6 months from 'picking & processing', and fully accept that processing can often include resting. I think you'll agree that traditional packaging and shipping (eg. sea freight in hessian sacks) has typically done no favours to Australian buyers, and that last season's landed crop from an origin will rarely if ever taste better than the previous one when cupped side by site (assuming no major crop-affecting factors).
What this tells me is age can be less of a factor compared to original bean quality and roast performance.
So we both agree that age can turn beans flat?
My experience is a loss of complexity, with my basic coffee chemistry thinking being that it is a result of the more volatile/less stable compounds degrading over time. It seems to me that while this will usually
result in a less enjoyable end product, there will be exceptions (maybe especially in coffees that cup a little lower due to the presence of less pleasant relatively volatile compounds).
The reason I eulogise the high end of specialty coffee (90+) and try not to buy anything less than 85 points unless it roasts up really well to a specific profile is because if you start with high bean quality, ageing and non-optimal roasting will still leave you with a much better cup.
eg. (MaxBQ - RoastError - Degradation) = CupQuality.
You make a good point that some coffees seem to need to 'stablise' before they roast brilliantly, but all will degrade after that I guess.