Hi John-
I've only been using the clay saucer (w/ sand) for a few cooks now, but I use it any time I used to use water, and I remove it when I would not use water.
The saucer adds a mass to soak up and store heat, and you don't necessarily want that when doing a shorter hotter cook. For those I have been going with an empty foiled water pan, so as much heat as possible is applied to the meat.
Sound like a nice variety on the menu!