Your senses are the best tools for determining if your tallow is still good. Before using a balm that you've had for a while, perform a quick check for these signs of spoilage.
No, it is not strictly necessary. sort of, whipped tallow is naturally shelf-stable and will last for many months at a cool room temperature. However, refrigeration is highly recommended if you live in a hot climate or if you want to extend its shelf life to a year or more.
No, a grainy texture is not a sign of spoilage. It is usually caused by temperature fluctuations. When the tallow melts slightly and then re-solidifies slowly, different fatty acids can crystallize at different rates, creating a grainy feel. balm is still perfectly safe and effective to use. You can often fix it by gently melting the balm completely and then rapidly cooling it in the refrigerator to re-solidify it smoothly.
Using rancid tallow is not recommended. Rancid oils have undergone oxidation, which breaks down the beneficial fatty acids and creates free radicals. Applying it to your skin can potentially cause irritation, breakouts, or inflammation and will not provide the nourishing benefits of fresh tallow.
The shelf life of whipped tallow isn't a fixed number; several factors can either extend its freshness or cause it to spoil prematurely. Being aware of these can help you preserve your product.