This article examines the time between product development and market launch, and its relation to the subsequent diffusion of consumer durables. We find that this "incubation time" is long. Further, it is a useful predictor of the shape of the subsequent sales diffusion curve. Using the Bass model as a base, we find that the longer the incubation time, the lower the coefficient of innovation (p) and the longer the time to peak sales. Further, using the incubation time in a Bayesian forecasting model significantly improves forecasts early in the life cycle.