SN expiration date

[Nymph]

Hello,
How long does SN keep it's effects? I read of the site that it will last 2 years if it's kept in good condition but after that they said that it pretty much never expires, so I'm confused. I need to know how long I can store it before it stops "being fatal" lol not sure how to phrase it
I'm gonna copy what it says exactly:
Cz: Datum minimální trvanlivosti: 2 roky, v podstatě neomezeně použitelné.
Eng translate: Date of minimum durability: 2 years, essentially indefinitely applicable.

 

[Living sucks]

If kept in cool dry place it can last many years. After 5 i personally would buy new.