While you may find some great deals right before the start of an event, it's always a good idea to purchase your tickets as early as possible to ensure you get your desired seats. If you do decide to purchase tickets last minute, many sellers will still have their remaining inventory listed through the first hour or so of the event.
Please remember that it's important to be aware of the delivery method and time it would take to receive the tickets when purchasing them this late and that if you purchase tickets after the event has started that you may miss some of the performance.