There are a few things that you can do to improve the shelf life of your cask ale though.
The most basic one is the buy Pins as opposed to Firkins. Shifting 4.5 gallons is a more reasonable proposition, in cask shy Ireland.
Another is the use a cask breather.
I know CAMRA don't like these things, but they don't operate in the republic of Ireland and frankly, their objections are just plain daft.
Explanation: A cask breather is simply an on demand valve, hooked up to a co2 cylinder. It replaces the volume of beer dispensed from the cask, with can equal volume of co2, at atmospheric pressure. As air is not dawn into the cask, oxidation of the beer is prevented and beer spoilage bacteria are excluded. This has the effect of increasing the life span of a cask.
All other elements of cask ale (stillage, venting, etc.) are the same.
Many CAMRA members have no problem with cask breathers, but the more vocal traditionalists (beard and sandals brigade) oppose it as “extraneous co2”.