For the SSC (Smart String Controller) RJ limited the node count to 128 because of the power concerns.
This is in a LE discussion group, so I assume the question refer to the LE and not SSC. The LE provides 110V power to the 16 channels, so the count is not a factor, it is the amps. The amps is dependent on the strings you are using and the numbers of those strings. So, there is no fixed number.
Steve