Hello James,
User aborzenkov is absolutely correct. You do not need to take the recommended training to take an exam (but it is recommended). You can schedule any NetApp exam at anytime through Pearson VUE (www.pearsonvue.com/netapp).
Regarding exam vouchers, they are periodically offered along with certain courses, but a voucher is not required to take the exam. You will need to pay for the exam without a voucher ($150 USD).
Also, it is your responsibility to ensure that your user information is accurate (email address, company) if you are taking an exam for compliance purposes.
Finally, if you have any additional certification questions, please contact ncp@netapp.com and you will receive a response within 2-3 business days.
Let me know if you have any other questions.
Greg Hyman
NetApp Certification and Accreditation Program Manager
ghyman@netapp.com