In my opinion, one must occasionally clean there saddles between treatments of saddle dressing. Be it Poofhide or a traditional saddle (horse) dressing. A simple cleaning once a year with saddle soap should do it.
In dry weather (like out here in Tucson) one needs to apply a dressing two to three times a year to prevent drying of the leather fibers.
In wet weather dressings are not needed as much except if one was to get the saddle soaked from rain. The water floats off the oils in the leather and therefore needs replenishing from a dressing.
Dressing such as Poofhide and R.H. Williams are tallow based heavy dressings that provide moisture and some level of water resistance. Oils, such as neetsfoot and the like should only be used for initial break-in or for a heavily damage and cracked saddle.