Some times we gotta do what we gotta do... which you will see where I'm coming from if you look at my station picture on http://www.qrz.com/db/k7zrz
. At times I have a Clippertion L amp down there on the bottom. I have never had a problem with heat, but then I don't do contesting or long winded transmitting of any kind. Everyone's situation is different, but everyone should consider the points that you bring up and do the best they can to provide enough ventilation.
p.s. My station is in my Motorhome.