Below will describe if Gift Cards/vouchers expire - and where you can change these settings.
Expiry
By default the system sets a 6 month expiry on Gift cards/vouchers.
To change this setting go:
Manager -> Settings
Then click on General Settings
Here you can change the voucher expiry default setting (see point 1. below) and then click Save
Valid
Although this expiry is set - the system will still honour and process cards after this expiry date. It would be at the salons discretion whether they want to accept it or not.