Carriers typical undergo a service life extension overhaul (think overhaul the whole ship, stem to stern) in conjunction with refueling. The 46 month figure is

Carriers typical undergo a service life extension overhaul (think overhaul the whole ship, stem to stern) in conjunction with refueling. The 46 month figure is for a RCOH (Refueling and Complex OverHaul). Subs can and are refueled much more quickly (and in many cases more often).