These are the reasons that I think Chad Cordero is still a solid reliever and will be for all of his career.
1) Has Consistent Control. Very rarely has problems walking people. Normally comes in and throws strikes.
2) Now has 3 1/2 years of major league experience as a closer. Has made the unusual jump from College to the Majors and has gained valuable experience being a closer. Other than the first six weeks of this year, he has closed at a rate 85% that puts him in the top 5 of any closer with 100 saves or more.
3)Does not get Hurt! This seems to be happening to almost every pitcher in the major leagues. Since he uses his legs so much in his delivery he has protected his elbow and shoulder against injury.
4)Still young. Has 2 years after this year before FA. There is every reason to believe he will get better and he is still Nats property throught 09 season. They could still get two more good seasons out of him before needing to trade him in July 09 if we are not in the pennant race or decide to not sign him.
5)He could still develop a Change-up. Remember Hoffman did not start his career throwing change-up as most pitchers do not. Cordero has gotten by with 90 mile an hour fastball and a slider. If he starter changing speeds he would become even better.
I can agree with most of your points, but I'd like to give three reasons why he is not a dominant closer(anymore):
1. He does not have a dominant Fastball and Hitters have finally figured that out. through all of 2005 he got by on being "sneaky fast" with a 91mph fastball. He's not "sneaky" anymore and he's never really been "fast". you might be thinking about Trevor Hoffman at this point....which leads me to my 2nd reason...
2. He is a big time fly-ball pitcher. that combined with his less-than average fastball leads to giving up a lot of HRs.
3. He has a very limited arsenal for someone without a dominant fastball. He's pretty much got a Fastball and a Slider. that is a power pitcher's arsenal, except Chad isn't one. Trevor Hoffman, by comparison, *can* throw a fastball, a cut fastball, a changeup, a curve, and a slider, and he developed his arsenal once his days of fireballing were over and it has extended his career.
there are my reasons, debate them if you will. I only used Trevor Hoffman as an example because his name was brought up in the original post.