How long could the Iowa class have remained active?

If the Iowa class had not retired in the early 1990s, how late could it have remained in service?

Probably into the 2000s, perhaps the 2010s for one or two ships with gentle use and rotating upgrades; further life would demand extensive rebuilding.

Keeping all four ships and rotating their upgrades could have extended service into the 2000s if they were used gently. One or two might have lasted into the 2010s. Salt-water deterioration would eventually require renewed hull plating, and re-engining would become attractive. Extending their lives further would mean a major reconstruction that left relatively little original structure beyond armor and guns. One suggested weapons change is removing at least the after turret and using its protected space as a missile magazine.