I really dig your artwork, not just the technique but I love the atmosphere through colour, too!
You could always try working on a side illustration and experiment with new means of painting? I normally paint my BGs and a /lot/ of time went into them. Recently though I found a way where I can "paint" things in a much faster method by using a form of cel-shading. Really when you get down to it, placing the right colours in the right areas is really what pulls off the illusion of depth, light and form. When I realized colour placement took precedence rather than just blending things for shadow and lighting, it increased my productivity ten fold. For example;
I was able to paint this image in a day:
Compared to this which took a few weeks at the time:
Granted it's only increased speed on subjects I'm familiar with, still need to spend time learning the texture of new objects. The above might be too messy for you, I know it is for me. But it's at least a proof of concept that once you place down your colours, you only need to spend a little time smoothing it out and you should still be able to get some painterly feel all the same. I don't think it's nearly a matter of simplifying overall style as it just simplifying your approach. (I'll still use blending as a basic gradient underneath, but then use cel-shading to flat in details on top.)
I really think focusing on colour placement will speed up everything overall. :>
(It looks like that's what the artist of Unsounded does as well. Subjects only have colours that denote basic shadow and light placement, not much beyond that. Which is all that's truly needed.)
Here I found an article on painting, where one artist is using a technique called 'tiling' to just lay down her values first of all like a map. Then works on top of it to bring it together.
"Ann Manry Kenyon is a direct, or alla prima painter, which means she likes to complete a portrait while the oil paints are still wet. This allows her to lay down thin patches of color mixtures and then blend them together as she refines the portrait.
Some artists refer to those brushstokes of color as tiles—disconnected marks indicating the appropriate shapes, values and colors that can eventually be brought together to create the appearance of skin, hair, clothing, etc."
Anything like this will increase your efficiency.