Shoe treeing - where do you draw the line?

I expect most here use shoe trees, at minimum for traditional dress shoes. I was curious to what extent that is extended to non-dress shoes, boots, etc. I use them in my AE Dundees and Shaker Heights, for example, but I don't usually bother for my boat shoes, Sebago camp boots, or Danner Explorer hiking boots.

Shoe treeing - where do you draw the line?