At least an hour to eat. It just depends on your group. Also, the last two times we ate there, we waited nearly 30 minutes past our ADR time before being seated.
We are staying at the Poly and want to eat either there or Kona on our nap break before we head back to MK. We are going back to the MK after dinner. We are only there two nights. Maybe the first night we should eat at Ohana's and the second Kona.
We were there for a little over 2 hours but we also watched fireworks so we took a little more time. I would say we probably could have been out of there in an hour if we hustled but after a long day at the parks, we were in no mood to hurry.