Despite all the attention that you bring to the conservation of natural products, the expiry dates are important to respect. Why ?
Because some active ingredients degrade in light, with the effect of oxygen, temperature or humidity, some are relatively quickly invaded by bacteria... All these factors will degrade or end up rendering the active ingredients ineffective. Much more troublesome, when certain bacteria colonize the preparation, there is a risk for your animal.
So always be vigilant not only to respect the dates and deadlines on your packaging or bottle and follow the storage instructions.
FYI and because I see it very often, ear solutions and eye drops (ear and eye drops) need to be sterile because they come into direct contact with the inner ear and eye respectively. They can only be kept for one month after opening (unless packaged in a bottle designed for storage and which specifies otherwise).