The Ninja hasn't had a major redesign since around '94. They basically just crank out a "new" version of the Ninja every year with a different set of colors.
A 2001 bike will have more parts that fail than a 2007. As parts on a bike get old, they wear out and need replacement. My '02 SV has had a few things replaced already... mainly gaskets and seals that simply wear out over time.