Depending on the environment you live in, and if the paint is prepped properly, Souverän will generally give you 8-12 weeks of protection and shine, if applied and maintained properly, before it needs to be re-applied.
If you've applied 3 coats and it appears that the jar is now only half full, you are applying the product way, way too thick. I have a jar that I've used about 6 times and you can hardly tell any is missing. The wax goes on extremely thin and it is not necessary to apply it thick. If you use a pre-wax polish prior to applying the wax, it will go on much easier and applying a thin, even coat will also be easier. Depending on the size of the vehicle, one 8oz jar is enough for 25-35 applications. Thin, thin, thin!
Souverän is a great wax for all colors, but it is known for its darkening ability on certain paints, more so red and black. It's a common misconception that Souverän is "only good" for darker colors and will not do much for lighter colors or those with a metallic flake. That's not correct. I've used it on a wide variety of different colors with stunning results each time, but when applied to black or red, it appears as if you are looking in to a pool of wet paint.