The warming function in Maxim only takes a few mins, so I just get it going while I'm covering up the scope - so it's no extra hassle for me.
Interestingly, the datasheet for the KAF-8300 says to "avoid sudden temperature changes". The manufacturer's rated minimum operating temperature is -10 deg C... which I guess most of us using this chip would easily go under in Winter.
http://www.kodak.com/ek/uploadedFile...00LongSpec.pdf