As I get evermore proficient with SketchUp I find it really doesn't take me long to build something up in general terms. The detailing takes longer simply because it gets a bit more complex and there's more of it than the general overall shape. I've gotten to the point where it really doesn't take me too long to figure out how to build something even as I get into more complex shapes.
If you're unfamiliar with 3D modelling I can tell you it shares one thing very much like building a physical model from scratch (as opposed to a plastic model kit with prefabricated parts). In 3D, just like with a physical scratch build, you have to build every single part or element from scratch and then put them all together. If you have identical or mirror elements then you need build it only once and make identical copies of it which does save you some time.
More on point, though, with my current project I built up the major components within the framework of a few hours. Like any hobby I work on it a bit at a time then take a break to come back later and pickup where I left off.
This is how the model presently stands. I'm trying for a mix of symmetrical and asymmetrical detailing to make it more visually interesting.