I sincerely doubt that the Souveran would "layer" to the point that you'd get an undesirable build-up, but I have had that happen (with a different LSP) on a garage queen that was waxed more than it was driven. For practical purposes, I'd go ahead and apply Souveran (to a *clean* car) as often as you like. That's what I do with the XJS.
I would, however, always wash the car before waxing. I just don't trust QDing to a) not mar the finish and, b) get things as clean as I'd like them. Anything other than "garage dust" I'd wash off with conventional methods. When I get the XJS out this spring I'm gonna wash it even though it only has a *very* slight amount of dust on it from being in the garage, uncovered, all winter. Better safe than sorry.
If it's actually been driven, and did pick up some road debris, I'd try *very gently* spot-claying it and see if the clay picks up anything. If so, clay it (again, be *very* gentle) before adding more LSP. FWIW, I almost always do some claying before I apply any LSP just to make sure I don't wax/seal in any dirt.