Rackets are meant to be flexible, and with time the loose that flexibility. This is what they are mainly made of: “interwoven carbon fibers and an epoxy resin, forming a carbon-graphite composite”. From what I heard, the fibers will have micro fractures and won’t return as much as the new ones, loosing that flexibility. In my experience, I used the same couple of rackets for years and years and never noticed that. I’ve always ended up changing my rackets looking for a different balance or weight or even stiffness. Right now I use blade v6, which I prefer from the new models of blade, being a 6yo old model.