As noted in the article, many home brewing yeast farmers extend the 'recommended' storage times for each of the various techniques mentioned.
Small amounts of yeast can remain viable for many months when stored under beer.
When using agar slants, although a fair amount of autolysis is noticed after a few months, it is usually possible to reculture and reuse agar slants a year old.
However, once they have been made, yeast stored in small samples of distilled water take up very little room and should be easy to store and reuse (especially if there are a number of yeast strains to be maintained) over long periods of time.
The Brewing Techniques magazine article "A Simple,Practical Method for Long Term Storage of Yeast" is not available on the Brewing Techniques website, but there may scanned copies of the individual article available via file sharing sites/services.
Edited by Wolfy, 23 July 2010 - 08:35 AM.