What does the term shelf life mean in regard to Titebond Wood Glues?
Shelf life is a conservative estimate of the minimum time period that we would expect a given product to remain usable, when stored as directed. This concept might also be called "usable service life" or "storage life", and it necessarily refers to both the physical handling properties and the ability of the product to perform properly. When used in reference to wood glues, reaching the stated shelf life does not mean that a product will "expire" or become unusable. Instead, we view the stated shelf life of most of our glues merely as a guideline to avoid potential aging concerns. In reality, as long as products like Titebond Original, Titebond II and Titebond III remain fluid, without drastic change in appearance, they will continue to perform as intended.
Information above, is directly from Titebond.