After 120 days from opening, stored in the refrigerator, Better Mayo is still microbiologically and chemically very stable. On a sensory level, however, the aroma is disappearing, giving way to slightly acidic hints. On the flavor side we are also seeing a slight loss of flavor. The texture is still creamy. So after 120 days the product is still in perfect condition, but it is starting to lose some flavor.
Clearly, the product will keep perfectly if clean cutlery is always used to take it from the jar.

What preserves mayonnaise is acidity. Clearly the coldness of the refrigerator also helps! When deciding whether a product is still good to eat, the same rule always applies: observe, do you see something strange-mold or something else? Smell, does it smell? If the answers are no, the product is edible.
The expiration date was invented 50 years ago. We have been using our senses for millions of years to tell if a food is edible.