Help to calculate heat dissipation on plastic dual in line DIP package (DIP-8 opamp)
The issue with this math is it works in theory, but in practice it may be widely off.

The math only works if all 60 op-amps work exactly in unison. That is a big ask. Any propagation delay in the input signal from the first to last op-amp will create a standing wave of higher current through the devices. Moreover, variances in gain and slew rate from device to device will cause hot spots in your array. These effects will also add distortion into your resultant output signal.

These are the reasons we do not typically double up (or more) devices to increase current drive.