The age is more to do with the supply/demand factor....that's why most of them use 100L barrels. Basicly in 3 yrs they can have a whisky that has developed similar to an older whisky of say around 5+ yrs old. There would be a formula that could be worked out, generally speaking, to calculate the age equivalent in smaller barrels. I should point out that you would have to work on a constant, eg. A hogshead.
Here is an example....
The reference point - 200L Cask
so a 2L cask is 10%
10% of 10 yrs = 12 months
Remember that this is all ONLY a guide as many more factors influence the whisky other than age.
Cam in response to your point, I would have to disagree....
The weather is the most influential part of the ageing process....a whisky will very much vary if you say had a cask mature in a fairly stable enviroment...ie. temps. and humidity levels.....than a cask aged in an enviroment with extreme changes in the surrounding conditions...
When I have the $$$, I plan on having a number of wharehouse's in areas of great climate changes.
I am looking at the moment for property down on Port Phillip Bay, Geelong area. This is an area I believe can have a great positive influence on the ageing process.