@Bruce-0 Fat won’t necessarily go bad, but it will go rancid and give you an off-flavor. If it is going rancid, you will notice a change in smell, maybe a change in color, and it should be noticeably different than truly fresh meat. If it was not 100% fat, but still had a fair bit of protein on it, the lean/protein portion left will go bad before the fat does. My best suggestion is to treat it like other fresh meat and if you are not going to use it within a week or so, vac seal it or at least put in a more closed container and freeze it.