No need to go to the CTO. Call them and ask them for ticketing-by-mail. Or if you really like going to the CTO, or distrust mail, call them and make the reservation, then go to the CTO to have it ticketed.

The reservation itself stays until end of the following day. Price stays until end of current day. Note that these criteria are according to the time zone in which the reservation agent is sitting -- and many of them are in Honolulu. So if you're calling when it's before midnight in Honolulu but after midnight elsewhere, they'll perfectly understand if you say "sorry, I was looking to get someone in the eastern time zone" and call back again.

Note also that for ticket by mail, the price is guaranteed as long as they receive your cert within two weeks, and it's postmarked within 24 business hours of your having made the reservation.