The voucher is valid for minimum one year as of issuance. The exact validity period is mentioned on the voucher itself.
You need to use your voucher before this date in the travel shop. The date of departure of your new travel package can be at a later timing.
For example; you need to use your voucher before May 26th 2021. On May 25th, you book a travel package from October 2nd until October 9th 2021.