"Polyesters" is a huge category. PET in plastic bottles is also a polyester, and it can persist for hundreds of years because it's typically in a highly crystalline form that resists fragmentation.
I was talking about polyester fibers. They have multiple orders of magnitude higher surface-area-to-weight ratio.
There are very few good studies of the degradation rate, and they typically focus on bulk products rather than particulates. So we have to rely on indirect evidence, the concentration of nanoplastics near polluted locations typically stays steady rather than keeps increasing. It means that it's in a dynamic equilibrium.
Another data point is lignin. It's a bilogical polymer, but that is not biodegradable in bulk, unless you are a fungus. And fungi don't have some neat enzymes that can degrade it, they just blast it with peroxides. And yes, there are lignin nanoparticles and you can detect them in water. These nanoparticles also don't accumulate and they can be degraded by bacteria because of their high surface area. Even though bacteria can NOT degrade bulk lignin.
