A number of different, rf‐excited 3‐W cw CO2waveguide lasers have been built. Four of these lasers, after continuously working for 15 000–30 000 h, still yield about 70% of their original power output. The design variations cover N2‐ and CO‐bearing gas mixtures, as well as internal‐ and external‐capacitively coupled excitaton electrodes. A similar laser survived 50 000 5‐min‐ON/5‐min‐OFF cycles without significant mirror damage. We have not been able to find suitable cold cathodes that allow the building of longitudinally dc‐excited cw CO2waveguide lasers that work for such extended periods of time.