SnO2-based gas sensors have been widely accepted in hydrocarbon gas industries to detect gas concentration and leakage. They have already been installed at many gas facilities, including in arid climate regions. However, the degradation mechanism and expected lifetime of commercialized gas sensors at high temperatures have not been intensively studied in terms of resistance and response time, making it difficult to maintain and operate the sensors. Hence, we systematically examined the degradation mechanism of commercialized gas sensors and derived their expected lifetime under high temperatures. As the sensor is exposed to heat for more than 25 h, its response time begins to be delayed. After that, its maximum output voltage decreases, resulting in inaccurate gas concentration detection. This phenomenon occurs much faster as the temperature rises. This might be attributed to the poor mechanical adhesion of the SnO2 film after heat exposure. Reliability tests at various temperatures revealed that the commercialized gas sensors are expected to degrade 10–88 times faster than those stored at room temperature. Therefore, the more frequent monitoring and calibration of the gas sensor operating at high temperatures are highly recommended to reduce the risk of explosive and asphyxiant gases.