It is highly unusual that these power adapters are failing so quickly.
Since you claim that you are using official Apple chargers, and that the cables and ports are clean, and the cords still look physically fine, it sounds like something deeper is going on. When chargers fail this quickly, it often points to either a power quality issue (like inconsistent voltage from the outlet) or environmental stress (like heat, bending at the connector, or strain on the wire that’s not immediately visible). Even though the cords look good, tiny internal breaks near the ends — especially at the Lightning or USB-C connector — can cause inconsistent charging and eventual failure.
If you’re plugging into an extension cord, surge protector, or an older wall outlet, fluctuating current can slowly burn out the internal circuit inside the Apple power bricks. Also, if you often leave your charger plugged into the wall without it connected to a device, that "idling" state can wear the adapter down faster over time. Apple's chargers are well-built, but they're still sensitive to poor electrical conditions.
Finally, it’s rare, but a hardware defect in your iPhone or iPad could be prematurely wearing out these adapters too.