Bottles - How long will beer stay fresh?

Hi
I have been busy brewing beer and have about five different ones bottled, two in carboys and three planned to brew in the near future.

Of the five currently in the bottles, two have been in the bottles two months, and then one more a month, another two weeks etc.

I allow each batch to carb for a month before drinking. As I have a number of beers available, it will take me a month to finish a whole case of one style.

This is what I have noticed: As a beer has been in the bottle for two months, I at times detect an off taste that was not around in that styles earlier beers.

I store at room temp 68F (now approaching 70F in the summer) in a dark basement. Are these beers going bad?

Now, I have detected this in only a few bottles in a couple of styles. My concern is a trend going on and my total beer supply with about six cases in the bottle for less than a month. Also, I really do not want to stop brewing.

Any ideas?

Depending on the off-flavor, it could be bugs in your bottles, like wild yeasts. That would make the beer taste thin and overcarbonated. It could just be the beer aging, which sort of mellows and blends flavors, with the hop character fading over time.

I'd suggest checking your sanitation and, if possible, store the bottles cold - that tends to make them last longer by slowing down any biological and chemical reactions.

bottle 'freshness' is also variable on the beer you brewed. very light beers, like a witbier or a kolsch...are best drank while still young.

darker beers or those with a lot of alcohol, typically do better when aged longer and drank after a few months.

Hops also mellow out, especially the flavor adn aroma hops. sometimes a fresh IPA tastes grassy after month in the bottle...but after 2 months its almost a different (and better) beer.