I'm a firm believer that craft beer SHOULD vary some over time.
It's a CRAFT product, there are variations in the ingredents themselves from year over year. We can see this by looking at the alpha acid percentages for the same variety of hops from year to year and I'm sure malt reports would show similar variations.
Wine varies from year to year for the same product from the same vineyard, same vines, and with the same equipment and it's just expected and a part of the experience.
This obsession with having the exact same product time after time I think is counter to having a craft product. If you want insane consistency then guzzle your Budweiser or Guiness in quiet contentment. If you want craft beer, which may vary by year, season, and batch, the cost is often in that consistency; I think it's a trade-off that's well worth it.
(I agree quality control is a necessity for even consumer craft beer and many things can and should be made consistent; I just don't like to hear consistency used as a direct equivalent of "quality".)
0.02 Eur,
Adam