As far as i know Vray make use of either CPU or GPU (or both -Hybrid-) and not RAM while rendering.
Generally people ‘overuse’ some features of Vray that makes everlasting renders. Those can be related to material or render settings. For such bathroom scene it shouldn’t take more than 5-6 hours with your specs.
Some questions/suggestions to move on:
1- Are you using new Vray 3.6 (released yesterday) or 3.4 version?
2- Could you please share your render settings (Try Irradiance Map + Light Cache for Global illumination. Brute Force is way slower but more accurate)?
3- Are you using displacement or bump maps or caustics? Using excessive of these features can increase render times quite a lot. (Same goes for reflective and refractive surfaces.)
4- Refer to this official Vray manual to understand the features and their properties.
Note: Also make sure you everything is properly modeled and front faces are facing the camera.