Driving Multiple Balanced Audio Runs Off Single Differential Op-Amp Circuit
The limit will be the loading by the cable capacitances. You can amass 10s of nF of load capacitance if you use many long cables.
This would be like a load of only a few 100 Ohm at 20kHz and the opamp will eventually not be able to drive this due to the lack of output current capabilities, producing distortion.