I do understand that static fire helps discovering malfunctions, as explained in this answer. A launch exerts an important stress on rockets' engines (high temperature and pressure, vibrations,...) and, except for SpaceX's launchers and the space shuttle, there is no need to make the engine reliable enough to survive more than one launch (one ignition, a few minutes of full thrust).
One static fire represents a significant part of the number of ignitions it will handle in its entire life. The same reasoning goes for the number of seconds it will be running.
My reasoning is that a static fire puts a strain on the engine, and thus may decrease its life expectancy significantly. Am I right? Does the static fire reduce the engine's life expectancy and thus its reliability?