[Brent Deines]

There is a 2 year shelf life on Delta Kits windshield repair resins purchased in 15ml bottles, but we also offer an unconditional money back guarantee to the original purchaser if not completely satisfied, now matter when it was purchased.

Obviously that would not apply if you purchased it used from someone else, but as long as it has not been contaminated, left in the sun, repeatedly exposed to air, etc. it will last for many years. If a windshield repair resin is not the consistency documented for on the spec sheet, or if it is discolored, it is likely contaminated and should be discarded.