No, there is a pretty well-defined and easily-observed “bathtub” curve of mean time to failure over the lifespan of an airframe. Maintenance costs skyrocket after the programmed lifespan because our defense sustainment fundamentally does not work.

When all goes to plan, we buy a new platform and enough spare parts upfront (to be produced throughout the programmed lifespan) to use a jet for 20-30 years. 10-15 years before that, we are supposed to be looking at developing a replacement. Congress invariably balks at the cost and forces service life extensions down our throats, which ironically make our legacy platforms far more expensive to fly than any modern one.

Looking at the F-15E vs the F-35A for cost per flight hour (which factors in maintenance, parts, fuel, and other operating costs), the F-15E costs about $10K more (~$27K vs ~$18K). Most of this cost comes down to the DoD essentially having to duplicate much of the old supply chain which no longer exists for the Strike Eagle, and that aircraft is only about 40 years old.

Once past the programmed lifespan, a lot of the more niche components will no longer be procurable because the manufacturer either went under with no other customers or moved on to something else. We then have to invest an inordinate amount of time, technical expertise, and money into reverse-engineering our own parts and finding an alternate contractor (who can now essentially dictate their terms since we need the part) or building it in-house.

In the meantime, field units struggle with plummeting MC rates as parts become scarcer and jets break more often. When it gets really bad, we start seeing new breaks in systems or structures that were designed to last the entire service life, so there is minimal, if any, sustainment capability.

TL,DR: It’s far more economical to replace platforms every 2-3 decades than to string them along for 4-6 because we “can’t afford” to replace them.