A 2014 RAND Corp. study found that sustaining the current Minuteman III force with gradual upgrades is a relatively inexpensive way to retain current ICBM (Inter Continental Ballistic Missile) capabilities. The study also found that a new ICBM system would likely cost two to three times as much as incremental modernization and sustainment of the current ICBM system.
One constraint on the lifespan of the current system is the declining quantity of missile bodies due to required annual test launches. The Air Force conducts three tests per year, and the ICBM system program office has recommended increasing that to four times annually. It means a force of 420 operational ICBMs is not sustainable beyond 2030 without new units and the entire missile asset will be depleted by 2135, RAND said.