We have gone to Hawaii in the summertime without any problems - 35k for coach awards on United, and we did the 50k J awards on AA before they discontinued that award. (The old P100JJ or something to that effect.)

One time we pretty much did it last minute - about 6 weeks in advance, and got our award seats and Marriott 087 hotel award with no trouble. The other times we did it about 4-5 months in advance.

The few times I've even begun to query wintertime awards to Hawaii, I've found everything zeroed out for weeks at a time, with our favorite hotels sold out completely - forget about awards. But then again, I have never looked or booked 11 months out.

We like the summer in Hawaii - hotels are more liberal with upgrades, the popular activities are less crowded, and you can book good restaurants the same day with little trouble. I don't think Hawaii ever has a truly "off-peak" season, but I don't think I'd enjoy their "max-peak" season around the winter/spring holidays.