This work illustrates the difficulty of implementing an optimality paradigm while dealing with increasingly complex systems to address real world issues. After summing up research experience acquired from varied sources, taking us from infinite dimension control issues to applications in the fields of space, energy and the car industry, we focus on specific developments in long-term issues. As a result, we defend our conviction that optimality provides a necessary framework for anticipating the challenges of long-term modeling, and maintain that this approach must remain central to our research perspectives. However, in line with our French mindset and education, we consider that a discussion of this kind starts with a look at the major principles underlying optimality and their natural link with the study of dynamic systems.
