Hi Kyle,
Currently Netro does not support a max duration irrigation setting. To reduce the smart watering time, you can change to Eco mode or customized mode through Settings->zones->specific zone number->smart zone-enabled->Mode. You can also set up the Smart Zone level from Advanced to Basic and create your own programs. In this way, smart zone schedule will not override your own programmed schedule.
Thanks,
Wency
Netro Support