Interesting. Seems like the Northbound Worka has a relatively short shelf-life. This may be characteristic of certain naturals. I've experienced similar reduction in blueberry flavor with other naturals, like Ethiopian Idido. First time I bought bags of that one from a high-end roaster I was blown away by the blueberry flavor. Bags purchased a few weeks later weren't quite as powerful. Bags purchased after that had lost virtually all of the blueberry.
There was plenty of blueberry in the first 6-oz of the two 12-oz bags I ordered from Northbound. I froze the rest in chamber vacuum-sealed jars. Blueberry was still present in the first 6oz I defrosted, but little less so. The blueberry continued to decrease with each jar, until the last one, which had been in the freeze for a couple of months, lost all but a tad of the berry flavor.
As posted earlier, I also bought 10 lbs of the Worka greens from Northbound. I divided the beans into three vacuum-sealed bags. Two had as much vacuum and my sealer can do (90%+), and were frozen immediately. I roasted four batches from the third bag, then resealed it with only a partial vacuum. The best of the first four 175g (net 149g) batches had distinct blueberry flavor, but I didn't get it roasted quite as light as Northbound did, so it didn't have quite as much punch. The other three batches were way too dark and had virtually no fruit flavor. A few weeks later (yesterday), I roasted four more batches. It'll be interesting to see if there's been any deterioration in the greens in that time, and even more interesting to compare those roasts to roasts from the frozen greens, which should not have deteriorated at all.
I have a feeling Northbound doesn't freeze it's greens. George Howell swears that greens do deteriorate faster than many roasters think, so he freezes all of his greens. I suspect it's even more important to do that with naturals that can lose their distinctive flavor over time.