Show me data...because my personal experience shows that 3-6 months gives no real cardboard flavour, and if you bottle correctly it shouldn't oxidize at all.
Melanoidin only develops at near boiling, so i have no clue what you are implying there?
It really depends on the beer style as to what will age well. In general, hoppy beers are not meant to age as hop aroma and flavor dissipates quickly. Some bigger, more complex beers can take quite a bit of aging and still improve.
The biggest flaw I have noted in all of the competitions I have judged is oxidation. And some beers, like barley wine, oxidation is to be expected and is pleasant giving the beer a nice Sherry note. In younger and or lighter beers oxidation usually starts to present as a bit of staleness or some of that Sherry flavor.
It is almost impossible to not exhibit any signs of oxidation, no matter how careful you are. But in cases where it is not severe, it can add a bit of depth to the flavor.
For my IPAs and pale ales, I usually go grain to glass in about three weeks. Four medium gravity complex beers, like a stout it is more like 5 to 6 weeks. My lager generally are about four months old when consumed. A cream ill is generally best fairly fresh but a tiny bit of cold conditioning, say a week or two can really enhance the clean crisp flavor.
If a Brewer finds that a beer really needs weeks and weeks of aging to come together, there are things that can be done in the process like ensuring the proper fermentation temperature or the proper yeast amounts are pitched. Some cases, where there are a lot of complex flavors a beer will need time for the flavors to meld.
