[rktman]

The orbiters were only used a third of their design life cycle.

[central_va]

When the concept of the U.S. space station evolved into that of the International Space Station, which suffered from long delays and design changes before it could be completed, the service life of the Space Shuttle was extended several times until 2011 when it was finally retired — serving at least 15 years longer than it was originally designed to do.