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How does the lifetime of a technological civilization affect the Drake equation?

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Planet TOI 700e — extraterrestrial life An illustration of the Earth-size planet TOI 700e orbiting within the habitable zone of its star. The habitable zone is the area around a star where liquid water, and thus possibly life, can survive on a planet's surface. Its Earth-size sibling, TOI 700d, can be seen in the distance.

In the Drake equation, the factor $L$ represents the average lifetime of a technical civilization capable of interstellar radio communication. This parameter is a critical multiplier in determining $N$ , the number of such civilizations currently existing in the Milky Way Galaxy.12

Because $L$ is the final term in the equation, the total number of civilizations is directly proportional to the duration of their technological existence. If civilizations typically destroy themselves shortly after developing advanced technology—such as through the use of weapons of mass destruction— $L$ would be very small, potentially resulting in $N \approx 1$ , meaning we are effectively alone. Conversely, if civilizations can overcome these risks and persist for long periods, $L$ becomes large, which could imply that millions of technical civilizations exist throughout the galaxy.12

Ultimately, $L$ remains one of the most uncertain variables in astrobiology, as it depends on the long-term survival and stability of intelligent societies.12