Originally Posted by BootSpell
#1. Remove shoes and insert shoe trees immediately.
#2. Remove shoes and wait overnight (or 24 hours) b4 inserting shoe trees.
The idea is to keep the shoe from loosing shape. Your foot has the effect of moistening and warming up the leather, it may even stretch a bit. You don't want the leather to dry and cool back in on itself in a funky way. So you cram the shoe tree in there.
You don't want to leave the tree in there all the time as it may stretch the shoe too much. But this may only be for people like myself who have a generic one size shoe tree. If you get a well made one I doubt it will stretch the shoe in a bad way that you will notice if you leave it in.
I'd guess if you sweat heavily in your boot then letting it dry is more important that shoe treeing it right away. What kind of wear are you having? Try both ways.