Case studies and the case method of teaching and learning have demonstrated pedagogical benefits. Sustaining the effective and efficient development of cases requires strategies and methods that are proven and systematic. Waterloo Cases in Design Engineering (WCDE) is a unique program to enhance design engineering education by converting student coop work term reports into case studies and implementing them across all courses in the Faculty of Engineering curriculum. Cases have been implemented successfully, and show promise in addressing and demonstrating new Canadian Engineering Accreditation Board (CEAB) graduate attribute requirements. The case method also shows promise in integrating these required attributes by expressing real situations encountered in practice and allowing individual students and student teams to experience realistic challenges in a classroom setting. In addition to developing cases from work term reports, cases have been developed from student capstone project experiences, Master of Engineering (MEng) design project experiences, and directly from the experiences of our industry partners. The development strategies and methods used to ensure effective and timely development of cases varies depending on the source used. This paper describes the development methods used to successfully develop sustainable sources of engineering design case studies, and offers lessons-learned perspectives from our development and implementation experiences.