A ``mean‐time‐to‐failure'' measurement has been made on propagated magnetic bubble domain patterns. A Permalloy T‐bar field‐accessed circuit was used with two compositions of epitaxially grown magnetic garnet films. As the number of steps of propagation at 100 kHz increases, the bias field margins at constant drive field for error‐free propagation are observed to decrease. A reasonable extrapolation of the data taken on a specific circuit‐material combination operated near the center of the bias range at 100 kHz suggests that an error rate as low as 10−20per step is attainable. The effects of the circuit‐to‐garnet spacing and drive field magnitude are discussed, as well as the effects of ion implantation and crystal annealing.