This paper focuses on the description of the behavior of supercapacitors during over-temperature and over-voltage stresses and the consequent ageing processes. Specific physical evidences supporting the explanation of the experimental findings are provided and discussed in the paper. A method to distinguish between over-temperature and over-voltage post-faults of these storage devices is summarized and discussed. Additionally, new accelerated ageing phases and recovering phases are detected during combined high-pulsed Power Cycling and high-temperature Life endurance tests.