Nice image, I like it. Moody. I'm surprised it took 49 hours to render though (at this size? !!), what were your render settings. Theres not many times you'll need to go above a detail setting of 0.7 or 0.8, an AA setting of 7 or 8, together with a GI relativity detail and GI sample quality of 1. Cloud samples are more difficult to predict but a sample quality of 256 is usually sufficient. Also a real killer is having a 3D cloud layer between your camera and water layer, the light rays have a lot of calculations to contend with.
Keep up the good work
Richard
ps: I just saw your artworks on DA, I guess (not hard) you know all this already. lol