Negative electron affinity (NEA) photocathodes offer unprecedented capabilities as electron sources that promise to enable a new generation of microscopy and lithography instruments. Extremely low-energy spread and emission noise, high brightness, ultrafast blankerless switching, changeable emission area, and uniform multibeam emission are some of the advantages that this source offers. Their unique advantages in high-throughput multibeam applications have been discussed elsewhere. The main barrier to their widespread acceptance has been concern about lifetime and stability. A prototype electron gun based on NEA photocathodes has been constructed to demonstrate the performance, including stability, of NEA sources. Initial results, showing over 100 h of excellent stability from a single 2 mu m emission area, show the paramount importance of in situ recesiation in attaining long cathode lifetime.