The HMC7357 datasheet does not include MTTF information however the HMC998APM5E datasheet indicates a channel temperature of 175C to maintain a 1 million hour MTTF.  Both devices are GaAs pHEMT MMIC amplifiers however the HMC998APM5E is wideband and operates at a higher drain voltage.  Can one assume the MTTF for the HMC7357 is 1 million hours for a channel temperature of 175C?