Required Number of Faces Per Cluster Value for S2S Radiation Model

How much number of faces per cluster value should be used for S2S radiation model in Ansys Fluent software?

For the face to face option while using the S2S radiation model in Fluent software, the number of faces per cluster needs to be defined as user input.
The solver clubs these many number of elements on a surface and stores their weighted average value of view factors as the cluster view factor for radiation heat transfer calculations
These number of faces per cluster should be defined considering different parameters:

1) The mesh resolution (surface mesh elements); lower the value for coarser mesh and vice versa.
2) The temperature gradient expected (lower value for high gradients).
3) Parts shape/geometry (lower the value of complex shape parts, etc.).