Your description of the tears occuring at regular intervals reminds me of failures I have seen caused by a failed rimstrip... although these obviously happen along the inside.

Also, defective tubes (which I am told do happen but never to me as fare as I can recall) generally do not last months before failing.

Do you have a picture of the holes?

Edit: Also, very odd that there are multiple failure points... one hole is enough to let the air out, and with no air pressure there is nothing pushing the tube against something that could cause a flat.