The Titan IV has been an expensive and troublesome booster. It uses very toxic chemicals for the propellants. It has an unfortunate rate of failure. It's time to move on.

We can hope the new Atlas V Heavy and Delta IV Heavy boosters will work as advertised. They were built to cost a lot less than the Titan IV with equal or better payloads, although the point about a lower launch rate could kill the cost advantage. They use much cleaner propellants. They use a common design between the core vehicle and the strap ons that should reduce the tendency of the engineers to "hobby shop" each launch. Time will tell.