Earlier quoted context omitted.
There were hints of it even back in the Apple II and Apple III era, both of which released with inadaquate cooling.
The only 8-bit Apple that suffered from inadequate cooling was the III. An average II would never overheat. You could, of course, load your II to a limit it'd fail, but my //e was fairly loaded (320k of RAM, SSC, Grappler, Microsoft Softcard (1 MHz Z-80), AE clock, Disk II and a PAL-M board). The II+ had mostly the same configs, with 64K and a Videx 80-column card in dual-head configuration. Both ran warm-ish for abo…
Having pulled a //e out of storage, that's all still true, FWIW. (I need to recap that machine one day soon.)