Multiple unibody cables failed in same MBP (13 in, mid-2012)

Hello,

I've had my Macbook Pro (13 inch, mid 2012) for a couple of years now (warranty is expired).

I had the "question mark folder" appear on my MBP the first time, tested the hard drive with a docking station, and concluded that the issue must have been the internal cable connecting the hard drive to the motherboard.

So I ordered up another one and installed it fairly painlessly, and my system worked fine again for about a month.

The very same issue occurred again, and my conclusion from this was that the seller I bought the unibody cable from must have simply salvaged it from a dead machine and sold it as new, so it was bound to fail. I ordered up another cable, installed it, and the computer was working again.

This time, however, the laptop only made it about five days before failing again.

The hard drive is still accessible from an external docking station, which leads me to believe that if the HD is corrupted it is only in a way that causes it to damage the connection with the wire, not the data it contains. Is this theory plausible? Should I just keep replacing the cables? They are fairly cheap but if this happened even once more I think I'd just give up on the laptop. Could I avoid this by replacing the hard drive and the cable or is the issue just as likely with the logic/motherboard? Obviously if I could resolve the issue long-term by getting a new hard drive this would be much cheaper than replacing the entire macbook.

If it helps anybody, the laptop is used very frequently and is very mobile (college student majoring in Computer Science). I've been very conscientious about where I let my laptop charge, since the first time this issue occurred it was charging in a fairly enclosed space which seemed to have caused heat damage to the unibody cable. This leads me to another question, could my laptop's heat regulation be off in some way? I dust it regularly so the excess heat is not caused by that. Anybody with experience in a similar issue or just helpful knowledge in general, your assistance will be much appreciated.

Thank you