Payment voucher numbers are generated at point of payment.
I don't know if they have any expiry date after issue. Probably not, since they're basically gift cards. And no expiry date is declared on the vouchers or the receipts. I've used some before which had been purchased months earlier.
Moving Payment Vouchers into Self-Serve account balance seems to apply the funds almost instantly. At most a few minutes delay. Suspended phone service usually resumes immediately, even if the information reported on Self-Serve webpage needs a little longer to get updated. Sometimes it doesn't automatically "renew" (start a new cycle) on your plan for whatever reason, you need to click "reactivate plan" yourself.
No charges are applied for account suspension or reactivation, and you don't have to pay for your plan while it's suspended. You just don't get phone service or Rewards while the account status is suspended. Some people intentionally allow their accounts to become suspended when travelling/etc. Just be careful not to let it languish for too long because after being suspended for 90 days it becomes permanently terminated.
