Because the power consumption of consumer electronic products varies according to processor execution, which depends on software, thermal risk may be increased by software changes, including software updates or the installation of new applications, even after hardware development has been completed. In this paper, we first introduce a typical system-level thermal simulation model, coupling the activities within modules related to software, electrical parts, and mechanical structure. Then, we investigate a case study of thermal management in both the development and maintenance phases of the product lifecycle. Reusing the simulation model, the thermal risk of software changes that may cause an enormous number of variations can be efficiently evaluated.