My ipad is kept in a case with no screen saver. I plug it in every night to charge in same place. I came down this morning and theres a huge crack across the screen from corner to corner. It still works great but its bizarre , how did it suddenly appear. Would the cold night temperature have done it. Had ipad a year now, is it worth getting screen replaced by apple or shall i just use it till its worn out. This is my second ipad after regular ipad, never had this happen before.