Hello, no need for skimp nor reduce the number of polygons, you just need to convert your large detailed objects to proxies in the vray toolbar. that way in the viewport these objects will be replaced by a box or whatever you want them to be instead, and vray will still render the original object.
Geometry won’t have a lot of impact on vray’s render time, but too big textures will, so will they if they have displacement in their parameters. Remove displacement if you have on some of your texture and try again
Also check if setting the GPU for rendering instead of the (default) CPU improves anything