I was reading recently that Keyshot is designed to use the CPU and does not actually take advantage of a GPU like traditional rendering programs. Please keep in mind, your classification of 'slow' depends on several factors. i.e no. of materials, geometry, reflections, illumination, output size, resolution and so on, i.e. the number of calculations your computer must process. So the more you apply, the more it has to work through. Your Question (and answers) are posted endlessly allover forums but In my opinion, I humbly suggest you run a series of tests, gradually increasing your render options and settings on your machine to figure out it's 'slow' point. From there, you will be able to figure out how much time you are prepared to invest per rendering. Hope this helps.