Test plans, test processes, test cases, test data, test harnesses, and the communication paths required to report and fix problems are already available. Budgets and schedules can be reused from previous projects, and they are much more reliable. Configuration control boards, configuration management tools and procedures, management processes, and the overall software development process are in place, have been used before, and are robust, reliable, and responsive to the organization's special needs. Because of the commonality of the applications, personnel can be fluidly transferred among projects as required. Their expertise is applicable across the entire line.
Product lines enhance quality.
The more complicated the system, the higher the payoff for solving the vexing performance, distribution, reliability, and other engineering issues only once for the entire family. Clearly, product lines benefit the developing organization, but they also benefit acquirers of systems as well. Enjoying higher product quality. Lower acquisition cost. Reduced maintenance cost.