Targeted durability, not immortality, should be a design goal

During the design stage, it has been one of the best practices to design a robust system that lasts forever. Such practices result in overdesign (i.e., less mass, energy, and temporal efficiency). Also, products that last well beyond their useful life often cause environmental issues.

Technological obsolescence is another issue when a product is designed to outlast its technological life cycle. For example the contents and the functions in a cellular phone are changing much faster than the cellular phones resulting in many working (and in good condition) cellular phones being discarded. In one estimate, approximately 135 million cellular phones are discarded every year in US^^.

Targeting a fixed life of a component/system during the design phase requires significant amount of engineering effort in design, prototyping, and testing phases. In addition, technological obsolescence, customer duty cycle (bathtub curve), etc. should be considered.

It is essential to follow Systems Engineering process of cascading the requirements from system level to component level to all the way to material requirements and then testing from material level all the up to the system level to achieve a design with a targeted life. If a component within a system has a longer life than the system, then the design should accommodate for easy removal and reuse or recycle of the component.

^^ http://www.electronicstakeback.com/wp-content/uploads/Facts_and_Figures_on_EWaste_and_Recycling.pdf