N9NEO wrote:

Are there any electrical engineers here that could tell me in a
quantifiable manner what exactly too hot really means?



That's a hard question to answer. The best I can do is 'It depends'.

Junction failure due to heat is of primary concern.

A couple of preliminary papers will get you going in the right direction:

http://www.nasa.gov/offices/oce/llis/0768.html

http://www.ewh.ieee.org/r10/bangalor..._18Mar2005.pdf

or:

http://tinyurl.com/2nz3jh



mike