This looks very nice Bob. Though I do have a couple of comments/suggestions. You know me huh

Your work becomes better and better so I'll be more critic/picky on you :p lol
I think next time you could concentrate more on renderquality rather than size.
Don't know what settings you've been using and how long it took to finish, but I think the image could use more atmo-samples and also higher render detail and AA.
The reason for the atmo-samples are the somewhat blocky shadows on the cacti and hills in the background. A low power fill light with an opposite heading of the main sun might also fill the shadows a bit more to show more detail. You can of course do this also by rendering it with higher GI quality settings but this would take lots of time.
Another way is to increase the strength on surfaces from the GI in the enviroment tab under the lighting button.
Yet another thing I've mentioned throughout your serie of pictures is that you don't use soft shadows, or at least at very low radius.
It isn't bugging me and it surely doesn't look bad at all but maybe your work will look even better with soft shadows

The vegetation look really really good, but I think the small bushes would really benefit and be more justified with higher render detail and high AA settings. They look a bit pixelated now.
I like the DOF-effect. In most images the result will look like the landscape is a miniature but you've managed to prevent that. Well done!
Is the DOF postwork or an alpha created in TG? I know how to do this now (Lucio taught me) and the results can be very nice and realistic.
So in overall very good work. You're working on a great serie and I don't understand the complaints of others to create an other serie of images.
Never seen anyone complain about NVSeal's orbital renders for example. And they shouldn't by the way

So I don't see the reason for it now.
I hope you'll find my suggestions useful and if you'd like to have some help or debate with me

lol....then you'll know where to find me!
Martin