The lifespan of a keg of beer depends on several factors, including whether the keg is sealed or tapped, the type of beer inside, the storage conditions, and the dispensing system used. An unopened keg that is properly refrigerated can usually last two to six months. Pasteurized beers—common among major commercial breweries—can stay fresh for up to six months when stored at a regular temperature of around 3 to 5°C (37 to 41°F). In contrast, unpasteurized beers, which are commonly made by smaller craft breweries, tend to have a shorter shelf life of about six to eight weeks, even under ideal refrigeration.

Once a keg is tapped, its freshness timeline can change significantly, depending on how it’s dispensed. If you're using a CO₂ system, like a kegerator or a bar tap setup, the beer can remain fresh for four to eight weeks after being tapped. This is because CO₂ maintains pressure and keeps oxygen outside, preserving carbonation and flavor. However, if the keg is tapped with a manual air pump (commonly used at parties), oxygen is introduced, and the beer will typically spoil within 8 to 12 hours.

For home systems like PerfectDraft, which use pressurized and refrigerated 6-liter kegs, beer can stay fresh for up to thirty days after tapping. These systems prevent oxygen exposure and maintain a stable temperature, significantly extending freshness.

Regardless of the system used, temperature control and cleanliness are essential. Beer that has gone bad may taste flat, sour, or metallic, and can appear cloudy or foam inconsistently. By keeping your keg cold, using the proper dispensing method, and ensuring sanitary conditions, you can maximize its shelf life and enjoy fresh beer for weeks—or even months.

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