Book the day you receive the voucher or it may cost more than you think
Two experiences bought, on both occasions had to pay an additional £25 pounds even when booking before the voucher expiry date. Problem is if the supplier of the experience has no dates available before the end date on the voucher you WILL have to stump up and additional £25 i.e. lose any cash back you gained. You are better off booking direct with the supplier and paying just a few pounds more.