I have nonrevved on HA but it's probably been a decade. I don't think there are amazing times to nonrev to Hawaii in general because it is such a popular destination so my advice would be to be flexible. If there are seats to HNL but not to KOA, take them because you can easily go inter-island. Don't try to travel home the day before you have to be back at work since Hawaii is a well known place to get stuck for a day or two - leave yourself a cushion.

All that being said, I have flown nonrev to the islands many times with no difficulty. Pretty much always at the beginning of March (see above, just before spring break) but I know people who have done it in April with no problems either. The off season (read that to mean the tail end of hurricane season) in October and the beginning of November would be a good time as well. Stay well away from long weekends and major holidays like Thanksgiving and Christmas. Have fun and let us know what you decide!