Humm, I recall seeing a GAO report (link was in this newsgroup some
time ago think) where the point was exactly the opposite. GAO wanted to
have spiral development and cited F-16 as a succesful example of it,
while project management was pressing for a finished product.

The reasons stated were in addition to reducing development risks that
a large number of aircraft in US inventory are getting old, and even a
minor delay in tight F-35 schedule has grave consequences for both
fighter availability and maintenance costs.
So if spiral development was used we would be a few versions into the
F-22 already being it would have entered service back in the early to
mid 90's and in the end the overall cost per plane would be much lower
as production scaled up. I'm sure the end of the Cold War had a lot to
do with the delaying of the F-22 project being a lot of the prelim work
had been done in the 80's when the AF voiced the need for a post F-15
air superiority fighter. Think about how glad Russia and China most be
that we delayed the F-22 so long they would not have to deal with the
F-22 threat for about an extra decade. In the meantime we have given
Russia a lot of time to come up with their own stealth aircraft and
counter-stealth technology whatever that may mean. We would also
already have a large lead towards an even more advanced fighter/UCAV to
enter service in the 2015-2020 time-frame. Now for the F-22 to be cost
effective its going to have to be around till 2025 and later being
production has jsut started and would be spread out over several years.
Talk about ****ing away a grand opportunity to truly leave Russia in
the dust with regard to generations ahead of them in fighter tech vs.
Cold War B.S. about how much better we were. We were better but a lot
of that was training being we were not flying against trained Russian
pilots but shotty 3rd world air forces with a few Ruskies in the mix to
add some flavor to the engagements.