The Press-pack IGBTs is ideally suited to applications where series operation is required; this quality is of particular interest for HVDC applications where several 100 devices may be required in a single switch. To ensure continued operation between maintenance cycles it is essential that the device fails to a stable short circuit. An experiment has been conducted and is reported in this paper to observe this characteristic over a period of 8000 hours. To simulate the real environment of an application selected die are pre-damaged in each device before encapsulation. The devices are then subjected to a large energy discharge after encapsulation. Results from the experiment show that the short circuit developed in the devices prior to the 8000 hour test remain stable, with voltage drops comparable to an operational device.