MM 40min sounds a bit long, it depends on your system power and what not. Im running a uh 4770k slightly overclocked with 16gigs ram. To speed things up you could drop the samples per pixel or mess with the FG settings. Make sure those inital FG points are not too high. Decreasing the Rays per FG might help too.
NOW if you have any standard materials present in the scene that could slow things down as well. On a full ship render maybe 30min max. I think my avg on the current destroyer model I am building is 10~20min max (for 1920X1080) depending on what elements are on screen and how big they are. Mostly it is my lum (glow) and translucent materials that eat up time.
One way to test is to utilize the material override (this will replace everything in the scene with whatever material is chosen.) I use this for AO passes or other things like wireframe renders etc. Just place your base hull material in there. If the time decreases drastically you likely have a incompatible material in the scene or something causing high calculations.
ALSO I see you have planar or unwraped textures this can add to calculations. AMT I find textures Actual bitmaps to really eat up render time more than say poly count. That and advanced surfacing. But a good example are super high rez planets with huge multi hundred meg image files will cause hours long render times.
BTW you might want to go into the object properties of the registry object and turn off cast shadows. This way itll look more like a painted element.
Oh I forgot to mention my omni I place Really far out to the point my model is just a speck on screen.
You might also want to look at exposure settings as MR really prefers to have that on. (rendering/exposure control) I use MR photographic with a GAMMA of 2.2 EV value of -0.6
Image control
Highlights 0.7
Mids 1
Shadows .75
whitepoint 6500k
Might vary for you.
BUT you might want to keep the result you have and just adjust in post. I know some who render out very flat images to avoid any clipping in either blacks or whites and then process the image in comp.
EG
So it is looking pretty good now and is quite useable output! Just need to ramp up the self ilum or just run a separate no light ship ilum pass only and overlay that in photoshop as additive to add in the glows.
Heck just colour select in ps works here is a full comp for laughs.

Grain is probably too much as I usually down sample by at least 3 to 4 times IE if it is a 1920 finished image Ill render it out at min 2time that rez. It gives a bit more control over effects. Also, it all depends on your tastes too.