Store sirloin steak in its original packaging in the coldest part of the refrigerator, where it will keep for three to four days. It may be frozen in this packaging for up to two weeks. For longer freezing, wrap in heavy-duty aluminum foil, freezer paper, or freezer bags. Securely wrapped sirloin steak will keep six to twelve months in the freezer. Defrost in the refrigerator, allowing 12 to 24 hours, depending on the size and number of steaks. Cook as soon as possible after defrosting.