title_body: How hot should an ESC get? What is the maximum safe temperature that a brushless drone ESC should get? What could happen if a brushless ESC were to go over its maximum temperature tolerance?
upvoted_answer: Like you said in your answer, it does depend on the ESC... so you definitely want to look into the specifications for your particular components.  However, to be safe, a good rule of thumb suggested on this forum is that you want to be able to put your finger on it without discomfort for five seconds.  If your reflex is to withdraw after only 2 seconds, chances are you're running a significant risk of overheating it.
  
  As to what happens if you exceed the temperature... it's not pretty.  Insulation on electric components starts to melt, resulting in shorts...  Overheating will typically result in a pretty instantaneous failure.
  
  It's always a good idea to keep your ESC exposed to a constant airflow.  If you put it inside a closed compartment, ensure that you have some way that airflow is being sent through that compartment.