Currently, about 150 CH-53E helicopters are in service with the Marines and another 28 MH-53Es are in service with the U.S Navy. The CH-53 requires 44 maintenance hours per flight hour. A flight hour costs about $20,000.[23]
https://en.wikipedia.org/wiki/Sikorsky_CH-53E_Super_Stallion
They were built in the late ‘70s and ‘80s?
If your suggesting it’s an old platform, I can tell you I worked on a Navy jet engine platform that flew in Vietnam, and the aircraft wasn’t retired until after 2000.......it was my experience working at a US Navy aircraft maintenance facility that they like to squeeze every flight hour they can out of their gear. 😏