We too use the AC a fair amount. On our last trip of 9 nights on a mono we racked up 100 generator hours. Sleeping is certainly a big part of it. But we also cook a fair amount on the boat. My wife does most of the cooking (not because I'm a bigot but because she does it better) and when we're not running the AC she refers to the kitchen as "hells kitchen". It's that hot. With the hatches open. The other benefit is that it dries the boat out. We take our towels - which will at best be merely damp hanging on the lifelines by morning - inside for the night and hang them up. By morning everything is nice and dry. We like that.

I can confirm the fuel usage. We calculated 1/3 gallon/hr.

My wife is from GA. Grew up without AC. And even she thinks it's hot without it. Do you "need" AC? Well... no. I'm sure you can survive without it just fine. And to a large degree it will depend on your tolerance for heat. If you like things hot, a boat with the hatches closed because it's raining will make you very happy.

Will AC likely make your trip more pleasant - no doubt.