Taler e-money is issued with a validity period. One month before the expiration date, your wallet should automatically exchange any digital cash that is about to expire for new digital cash with an extended validity period. However, if your wallet is offline for an extended period of time, it may be unable to do so. Ensure your wallet is regularly online to avoid losing money due to expiration!
Their very own FAQ says:
How to avoid digital cash expiration?
Taler e-money is issued with a validity period. One month before the expiration date, your wallet should automatically exchange any digital cash that is about to expire for new digital cash with an extended validity period. However, if your wallet is offline for an extended period of time, it may be unable to do so. Ensure your wallet is regularly online to avoid losing money due to expiration!