What is the design lifetime of JWST in years?

JWST’s designed science-mission lifetime was five years.

That figure refers to the planned period of scientific operations after launch, commissioning and calibration. Webb spent roughly six months after its December 2021 launch unfolding, cooling down and aligning its mirrors before beginning regular science observations in 2022.

The five-year design figure was not necessarily a hard expiration date. Mission planners also established a goal of ten years, dependent largely on the propellant needed for station-keeping around the Sun–Earth L2 point. Accurate launch and trajectory-correction burns left Webb with more fuel than originally expected, improving its prospects for extended operations.

This is why “five years” is the standard answer to the design-lifetime question, while ten years is better understood as an operational goal or expectation. Actual longevity can exceed the original design target if fuel, spacecraft systems and instruments remain healthy.