While not as likely on a 5 year old vehicle it is still possible, it's all about how many times they have been bent cycling the hatch up and down. Material fatigue in copper happens no matter what year a vehicle is. Work hardening will get the best of basically any metal. Do you use your hatch on a more than once a day basis? I'd imagine the average driver proper uses a hatch a few times every 2-3 days or so just getting groceries. If you are opening and closing your hatch 4x more than the average user of a 20 year old vehicle than you have introduced the same amount of fatigue on the wires as is present on the 20 year old vehicle. I personally don't use my hatch THAT often and I would guess neither did any of the POs because my 98 is still perfectly running on all hatch components (that said I wouldn't be shocked if something broke tomorrow, I haven't pulled my boot to actually check the condition of the wires).