Thughes,
There is only one way to find out!! Give it a shot and see.
Lengthy Post Follows!
Hashie,
Even though our wort in the cube isn't 'living' the flavours are still combining and balancing themselves as the cube is aged. Similar to stews and curries tasting better as they get older!
With the comment on HDPE being porous to oxygen molecules, I don't think you would see a cube inflated or blown up without something else sinister being in there first.
Experiment 1 - I have a cube at home I will intentionally put aside and mark the size of the air trapped in it and I will come back at monthly intervals and see how much it has grown. As a bonus, I'll include pics!
If the oxygen does get into the cube, it seems it isn't enough to cause any notable defects in our beers.
Example: Hashie and myself with 9mth old cubes and some of my local brewers have told me of their cubes being over 15mths old and fermenting fine.
Does anyone have a story of an old cube making undrinkable or only just-able-to-drink-beer?
Maybe the precursors are there and fermentation has been treated in such a way (correct temperatures, proper sanitation, good amount of healthy yeast etc) that any oxidation is so small that it is undetectable or doesn't develop any further.
John Palmer in 'How To Brew' talks of Hot Side Aeration
If the wort is exposed to oxygen at temperatures above 80°F (26°C), the beer will sooner or later develop wet cardboard or sherry-like flavors, depending on which compounds were oxidized.
It is a possibility that oxidised wort could affect the how long the resultant beer will stay/taste good for once it is packaged and stored for any length of time. My beer doesn't last long enough to find out!
Experiment 2 - I think this is a bit harder to test as I would want to store the wort for a year in a cube and then ferment it and see how it fairs after 6mths, 12mths etc in the bottle. I'll report back in 2014!
So, after all of that, what do I think of NC cubes that have been stored for a long time?
I produce double batches so regularly have extra cubes of brews sitting for long periods of time. I'll brew one of the cubes then brew a different beer to have some variety on offer.
In my experience, I am usually happier with the beer I have brewed from a NC cube that has been sitting for a length of time generally 3mths or more. I thought the flavours were more rounded and settled. Having said this, the time between tasting the beer from the first cube and the second one is generally about 1-3mths so time/my memory could distort what I thought I tasted in the first beer. I'll need to take some notes when tasting to have some sort of comparison.
I'll stop typing now so someone else can add their thoughts.
Cheers
HC