Here is shelf life from the FAQ section of the zaino site.
Sounds like you should finish it off this season then maybe start over.
I'm pretty sure you will fine with it especially since its the pro version.
Q: What is the usable shelf life of Zaino products?
A: A 70° room temperature is best for the longevity of Zaino products. Due to the optical additives used, extreme heat or cold can result in a decrease in gloss-enhancing properties.
When stored at average room temperature between 65° and 75° degrees, shelf life is as follows:
Z-PC 3+ years
Z-AIO 3+ years
Z-CS 5+ years
Z-1 For optimum results, use before 3 years.
Z-2 For optimum results, use before 3 years.
Z-3 For optimum results, use before 3 years.
Z-5 For optimum results, use before 3 years.
Z-6 5+ years
Z-7 5+ years
Z-8 5+ years
Z-9 5+ years
Z-10 For optimum results, use before 2 years.
Z-12 For optimum results, use before 2 years.
Z-14 For optimum results, use before 2 years.
Z-16 3 to 5 years
Z-18 5 years +
ZFX For optimum results, keep tightly capped, avoiding moisture. Use before 24 months.