I don't see anything wrong with the length of time, or the amount of vinegar that you used, though I don't generally use a vinegar in my soaking water for sheep casings. I don't know if you worked with sheep casings in the past, but they are very delicate, especially if you over stuff them they will split. I've had several blowouts during stuffing, let alone twisting them into links. I prefer sheep casings over collegian, but they are a pain to work with.
To eliminate the possibility that the vinegar may have deteriorated the sheep casings, don't use vinegar next time. I feel sheep casings don't need it.