Many people ask if synthetic deer urine expire or go bad. The best answer I can give is NO.
Synthetic deer urine formulas are superior to real urine in many ways. First is the fact that they will never get bacteria laden and break down like real urine will. In fact, after two to three months of even the best conditions, real urine spoils. It simply rots. Many of us have bought real urine scents from the big box stores. It was bottled many months before you got it because the supply chain moves too slowly in mass commerce. When you opened the bottle, it likely had a vile smell, was dark in color and wasn’t attractive to anything, including deer. You wasted your money. It may not have an expiration date on the bottle, but it certainly did expire. It went bad.
Excellent synthetic deer urine formulations are designed to be extremely attractive to deer, but do not contain bacteria or ingredients that will rapidly break down. In good conditions, or even non-ideal conditions, it will remain perfectly intact and ready for use. It will remain effective. Even under worse case scenarios, it won’t really go bad. If exposed to high heat over a long period, some chemicals may break down a bit, but they do not rot. It may reduce the effectiveness to some degree, but it will still work and will not frighten deer. If you leave the bottle open, you may lose some of the effective component of the scent, the volatile odor components that make the scent effective may leak out into the air as that is what they are designed to do. It will again reduce effectiveness, but not destroy the urine to the point it is bad.
To make sure your synthetic urine does not expire or go bad, simply store it in a reasonable manner. Keep the lid on tight. Keep in a reasonable temperature out of direct sunlight. Want to be cautious? Store it in the fridge as it surpassed all the requirements. But to be sure, if you leave it in a coat pocket, even until the next season, your synthetic deer urine scent will not go bad or expire. Simply use it just as you did the previous year.