Silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) are a key technology in mixed-signal, RF, and mm-Wave applications due to the combination of high performance and bandgap engineering with the high yield and low cost of classical silicon manufacturing. Conventional studies on the operational limits of these devices have centered around DC measurement, resulting in excessively conservative limits on biasing and operation. Additionally, these limits are set under a standard operating environment, which limits how well they can apply to extreme environments (for example, extreme high or low temperature). This work combines classical measurement techniques with custom test hardware and setups in order to investigate reliability at both the device and circuit level, and in extreme operating conditions. The goal is to enable reliability-aware circuit design by bridging the gap between a physics-level understanding of transistor reliablity and circuit- and application-specific understanding of performance-reliability tradeoffs, enabling designers to optimize system designs to achieve high performance without comprimising device lifetime.