All experiences need to be booked and taken by the expiry date printed on your voucher.
If you would like to book your experience after the expiry date, this is at the partner's discretion, however they are under no obligation to accept this if the voucher has expired or will expire before your experience date.
If the partner isn't willing to accept your booking after the expiry date and you won't be able to make a booking before your voucher expires, you can extend your voucher online here