Sound advice there, in my experience (at home, and at work).
I relocated my TP-Link 9980 earlier in the year, into a different room in a spot where there's not much airflow (but it's not a hot room, normally). Summer 2018 across the UK was warmer than usual, so I stood the W9980 on a couple of random objects to help ensure there was room for airfow. The gap underneath didn't help the 9980 temperature much (according to a non-contact thermometer), and there is now a separately-powered USB-powered fan nearby, to be switched on (manually) when the ambient temperature goes up significantly. The extra airflow from the fan does keep the router slightly cooler.
This action was prompted partly by an incident earlier in the year when my cheap+cheerful Humax Freesat box (HB1000S?) with an external USB drive started misbehaving, locking up occasionally, eventually ending up with a gentle whiff of hot metal and a Humax that wouldn't finish the power up sequence. 250GB of recordings are still visible as files when the USB hard drive is read from a "computer" rather than a Humax, but not playable as recordings because "decrypting" the content of the files seems to be keyed to the original (and now dead, and not repairable?) Humax box (I've had the lid off the Humax, "no user serviceable parts inside", etc - and a heatsink that's too small???).
Not nice; you have been warmed, don't let this happen to "your" recordings.