How long can a carbon fiber bicycle frame last?

Carbon fiber itself has almost no shelf life and does not rust like most metals used on bicycles.
There are usually five different grades of carbon fiber: low standard tensile modulus, standard tensile modulus, intermediate tensile modulus, high tensile modulus, and ultra-high tensile modulus.
As the level increases, the quality and price of carbon fiber will also improve.
Carbon fiber is classified according to its tensile modulus and tensile strength. The tensile modulus represents the rigidity of carbon fiber, measured in GPA. Tensile strength refers to the maximum force exerted when carbon fiber is pulled apart, expressed in units of MPA. (Mechanical properties of carbon fiber in the following chart)
Carbon fiber with ultra-high modulus has the strongest rigidity. However, carbon fibers with intermediate modulus have the strongest tensile strength, so under the same usage conditions, carbon fibers with intermediate modulus will have a longer lifespan.
Resin quality carbon fiber frame is not only made of carbon fiber, all these carbon fiber components must be glued together with resin.
The role played by this resin is more important than you imagine. Carbon fiber is actually a material fixed in place by resin, forming a hard and sturdy structure, namely the carbon fiber frame.
The manufacturing process of carbon fiber frame will be the biggest factor determining its service life.
You can have the strongest carbon fiber and resin, but if the manufacturing quality is poor, you will not be able to get much lifespan from carbon fiber bicycle frames.
The production process includes all aspects from the materials used to the curing process required to bond the resin to the carbon fiber.
Finally, the service life of the carbon fiber frame depends on the protective measures taken during the manufacturing process, namely the coating process.
The only thing that truly needs to protect carbon fiber is to avoid exposure to light.
Ultraviolet rays from the sun can almost damage any material that has been exposed for a long time. To address this issue, most manufacturers use UV resistant coatings and/or wax to protect bicycle frames.