What flavor is beer stored at room temperature for several months most likely to develop?

When beer is stored at room temperature for an extended period, especially if it is exposed to light, it is most likely to develop a paper-like or cardboard flavor. This off-flavor is typically associated with oxidation. Over time, oxygen can interact with compounds in the beer, leading to the breakdown of certain flavor compounds and the formation of new ones, which can create a stale or papery taste.

The presence of light, especially UV light, can additionally contribute to off-flavors by forming compounds known as “lightstruck” or skunky characteristics, which is often referred to as "skunk" flavor. However, that flavor specifically tends to be more connected to certain types of hops in beer, particularly when it comes to beer in clear or green bottles exposed to light. In contrast, a paper flavor is more consistent with oxidized beer, which naturally occurs with prolonged storage without proper conditions.

The other flavors, such as banana, rotten egg, and skunk, would arise under different specific conditions and are not common outcomes of simple long-term room temperature storage.