We have done several longer cruises, including this one. It was fabulous . Like you, we enjoy sea days as much as port days so this cruise was perfect.
HAL has the best laundry service at sea, imo, so no need to worry. Especially with the heat and humidity being able to send clothes out daily just enhances the vacation/cruise experience. We buy unlimited at $7 or $8 a day and it pays for itself many times over.
we prefer aft cabins for the quietness and the ability to watch the wake. I do not recall any rough seas except for when we left San Diego, which is normal.
we have extensive cruise history with both Celebrity and HAL and enjoy them both. HAL offers longer cruises and perhaps caters to a more “mature” (in age) crowd. Of course for a longer cruise the cruisers will likely be retired.
you are in for a treat.