The off-state conductance of a standard heat switch is approximately 37µW/K at a temperature of 4K. Heat switches are extremely delicate and cannot be used to provide mechanical support, indeed they MUST not be used in that way. For this reason we do not measure or specify the compressive and tensile strength. So far as lifetime is concerned, that is difficult to say as some heat switches give trouble-free operation for many years, while others do develop faults in a shorter period. We have approximately 2% failure rate overall for heat switches once they have been shipped. However we will provide free replacement under warranty for switches that fail in use due to manufacturing defects.