5 years is the entire time that the 990s went from being a concept to the end of their racing lifetime.
I don't know if you just want to argue for the sake of it, but believe me, in technology terms, 4 years is a looooong time.
These teams don't come fresh-faced in 2002/2003 and have to learn from scratch. They have decades of bike-building and tuning and racing expertise to call on.
Look at the ART, as an example. Barely more than a basic Superbike 9 races ago, lapping inside 2 seconds of the lap-record-breaking Honda last weekend.
Look at the Ducati - in less than a year they completely redesigned the bike from an 990 to an 800 and won a championship.
Sorry mate, but arguing that 4 years isn't a long time in racing terms is just plain wrong.