How long can Flourish Excel be stored?

[gu2high]

I am considering to buy large amount of Flourish Excel but don't know how long it can be stored.

I read in the forum that it will break in 24 hours in the tank, but if not used, how long can it be kept until expire?

 

[Zezmo]

Over a year and it still seems just fine. Just keep it in a dark cool place.