I've been reading some forums on probrewer.com, and there seems to be a consensus that bottle conditioned beer lasts longer than force carbonated beer. Why would that be?
It likely has to do with the fact that there is more yeast in bottle conditioned beer than in force carbed beer. The extra yeast scavenges oxygen and extends the shelf life of the beer.
Seems like a bit of a tempest in a teapot to me. Here are my thoughts, assuming an environment that is a cool constant temperature, dark, and dry.
The majority of beers, especially those brewed with spices and typical alcohol content, actually begin to lose flavor over time. These beers will have well passed their peak and declined considerably in flavor before it will go bad in the bottle.
Beers that benefit from long aging generally are highly hopped or have high alcohol content or both. The chance that those will go bad is low as well because of the preservative properties of the hops and alcohol.
I think there is a tendency to equate beer with wine when it comes to aging in a cellar. Some aging is necessary with beer, especially at higher ABV. But its not wine, its not scotch. Its not meant to last for a decade in the bottle. I think that's where discussions like this come from.
I don't know if having naturally carbonated (and the associated lees) will make a beer last less time or not. It's academic anyway, you shouldn't be keeping the beer that long.
I contend that with the properties of alcohol and hops plus good sanitization that the beer's flavor will fade long before it goes bad.