Duh, I guess I should have read the title! Yeah, great potential with that program. Have you tried switching the Lux material setting to "null" so it will not render? If you set the opacity to 0 in Daz, sometimes it will still render in Lux depending on what the other settings are.
Also, from Preta-3d's website, setting as unseen or 'null' anything that isn't actually visible in the render (in this case, for example, the model's tongue and teeth, as well as her feet (since they're concealed by her boots), will significantly reduce the rendering time.
You can set LuxRender (through reality) to stop rendering when it reaches a specified number of samples per pixel by setting a "Max Samples" slider to a non-zero value. With that slider in the default 0 position, LuxRender will not terminate a rendering job, it will instead continue to refine the light simulation. According to the Reality User's guide, 2000-3000 samples per pixel is generally considered a good starting point for quality images. Run a few renders and decide how many samples per pixel are required to meet your standards.