This chapter introduces the edited volume and distinguishes between traditional definitions of maintenance and generalization, modern definitions of maintenance, and the concept of durability. Examples are provided related to both treatment and training durability. Finally, the chapter ends with a call for the field to progress beyond goals of treatment or training effects simply persisting across different contexts or short periods of time and instead for treatment or training effects to remain durable during the robust challenges that exist in natural environments and daily situations for individuals with autism.