My Hurricane (2014) has a double pancake light installed vertically just behind passengers seat... As I use that seat for our seasonal trips as an 'office - the light got a lot of use. It definately doesn't vent properly in that orientation - and started to melt/discolor the clean plastic lens.
Definitely cooler on LED now.
Heat certainly not good - but long way from melting to ignition...
Some examples:
Melting points and ignition temperatures
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