If you are upgrading the AP that would typically mean upgrading the firmware and that will always require a reboot of the AP. If you are referring to pushing a configuration update to the AP, I'd suggest testing with a delta update on a single device first. If the delta fails then you know you need to push a complete upload that will require the AP to reboot. Today in HMNG (Extreme Cloud IQ) most configuration changes can be made with a delta update, but I'd suggest that any changes made to the ethernet interfaces of the AP or to the IP addressing of the AP be pushed as a complete update.
