The Dyna 2000 ignition module failed on my 89. Dyna tested it and replaced it,for a fee. But it was mounted in the fairing, directly above the oil cooler. It now resides in the tail, in a bed of neoprene.
I did not bother pursuing this the other day when Jools mentioned the OEM electronics were housed there (in response to my suggestion about it being too hot) but seeing as how it's been brought up again....
When manufacturers are hunting around for OEM components (from 3rd party suppliers) they issue a brief of performance criteria, in this case, one of them would be heat.
Manufacturers of after market accessories are bound by no such requirements. In fact, if you read the fine print (or sometimes the bold print) you will see they specifically mention choosing a mounting location away from excessive heat.
I have seen plenty fail, they distort, covers fall off leaving them prone to dust and moisture contamination or actual component failure. If the device has a potted circuit board, the potting material will often shrink and crack from the heat (allowing moisture or dust to short circuit the board) In my experience, dust seems to be a bigger problem than moisture.
The fact is, you will probably get away with mounting it anywhere, as I'm
sure someone will point out, but I have seen and fixed enough problems to play it safe on my own bike. As Sparky mentioned, an extra metre of wire is neither here nor there when it comes to voltage loss and if the wiring is secured, protected and joined properly, not an issue.
Maybe Mike could have use the CO2 cannisters he stores in the tail to cool his electrical melt down recently.

(just kidding Mike) Speaking of which, did you ever find what caused that?
IMO
Noel