I found my S-line wheels such a doddle to keep clean that I didn't really pay much attention.
They got the odd polish with Meguire's, but that was that.
My D3 wheels are a nightmare though (they look like the fan blades of a jet engine).
So I've recently started using poorboys wheel sealant, which comes highjly recommended.
Wash the wheels, dry the wheels, polish the wheels, coat them in poorboys.
Hopefully, three of four uses of this procedure will lead to them being dead easy to clean in the future.