With vaseline, you don't have to worry about shelf life. As long as the consistency is creamy, you can use it without hesitation. With leather balm, this is only true to a limited extent. When the balsam begins to break down (the emulsion no longer looks milky but forms grains or turns brown), we no longer recommend its use on high-quality bindings. The active ingredients against fungal attack are then no longer active enough. If the balm starts to smell rancid, you should discard it.