Avoid setting the Reflectance 0° color too bright. Setting it to 255 for example means this material will reflect back all the light it receives, which does not happen in the real world.
Maxwell Render still keeps the amount of light reflected/absorbed within physical limits but the result with such high Reflectance values means the light will keep bouncing around in your scene with very little loss in energy, which will produce noisier renders and a washed-out look with very little contrast.
A reasonable setting even for very bright materials would be around 225-230. For example, the Reflectance value of a white piece of paper, when converted to RGB, is around 225. Please note that this only matters for the Reflectance 0° color. The Reflectance 90° color can be left at fully white (RGB 255).
Left: unnaturally high Reflectance 0° at 255 results in loss of contrast, unrealistic shading and slightly more noise. Right: correct Reflectance 0° set at 225