Let's put it this way, my keg of Oktoberfest (in my signature) went on-tap in April of 2010. It still tastes fine (a bit of acetylaldehyde but that was there from day 1).
It has always been kept cold though.
Primary: English Mild
On tap: Pale Ale, Lancelot's Wheat, English Brown Ale, Steam Beer, HoovNuts IPA
Bottled: MOAM, Braggot, Raspberry Melomel, Merlot, Apfelwein, Pyment, Sweet mead, Cabernet
Gal in 2009: 27, Gal in 2010: 34, Gal in 2011: 13, Gal in 2012: 10