Got a set of DCI 990's from my father a while back, and been playing fairly consistent with them; I play to a 15 hcp. My question to Team Titleist is whats the popular opinion of the 990's and the advantage of upgrading?
You can get newer clubs, but I don't know if any of them will be an upgrade from the 990's.
990's are good irons, they play like blades because of the mass in the back. if you're consistent with them then its good, cause when you miss with them it shows and feels.
In terms of advantage in upgrading... its 10 years of new technology and improvements of difference. Better materials and design to help you hit the ball better. You could at least change the shaft as they are already old (maybe rust inside, etc.)
Hope this helps. Good luck