Walter Pall says, in an article on his blog, that with modern substrates over-watering is almost impossible. Those words make quite a difference. I, for example, have a juniper (or something) in a small pot that stays wet for a longer period of time than the trees in much bigger pots. There are many factors involved, I know, but usually there are exceptions from rules. We can't really know a thing for sure if we never tried it. Until this year I was scared of overwatering, but I found out that it's not that easy to do it.