Water Colour powder when stored correctly can last for many years. However it is best to use within two years of purchase if you can, to minimise the chance of it spoiling.
The last two numbers on the batch number (BN) are the year of manufacture.
It is important to store them somewhere dry, and ideally also cool and dark like a drawer or cupboard (do not store in the bathroom). Check the lids are on tight as this will help to prevent moisture getting in.
The dye should look powdery - if it looks granular then it has probably spoiled and may not work.
Our friendly support team are here to help, so please do contact us.