Dislocation glide velocities in GaAlAs/GaAs, InGaAsP/InP, and GaN-based light-emitting devices are estimated. These results are consistent with device degradation rates related to dislocation motion. It is clarified that the long lifetime of GaN-based devices with high dislocation density is principally due to extremely small dislocation mobility, partly due to small shear stress for dislocation motion, and due little to the radiation enhancement effect.