What people are saying about it?
Most electronic components dissipate heat whenever current flows through them. The amount of heat depends on the power, device characteristics, and circuit design.
How well does it model reality?
Besides the components, the resistance of the electrical connections, copper traces, and vias contribute to some heat, and power losses.
How many books have recommended it?
To avoid failures or circuit malfunctions, PCB designers should aim at producing PCBs that operated and remain within safe temperature limits. While some circuits will work without additional cooling, there are situations where adding heat sinks, cooling fans, or a combination of several mechanisms is inevitable.