The rear wing / spoiler could have been helping you, but probably not much. At best, the air behind our rear windows is rather turbulent. I noticed after 120k that my struts were getting soft, and the rears were pretty well shot. At highway speed, the car lacked stability, and the rear bobbed horribly under braking. I got a set of KYBs from SPS and, with an alignment, it is rock-solid again. I'd check your struts before you give too much credit to the rear spoiler.
I don't think spending energy on the wiper area will bring you much tangible result. Per reading, posts here, etc., I'd go after a flat bottom, flat wheelcovers, front wheel deflectors and the like first.
I'm registered on Saturnfans (Bman91SL2), but I'm not there much. I owe them a post because I tried a Marvel Mystery Oil flush and cured my oil consumption problem.
I only have 54k on the car. The struts are still nice and tight. The tires are getting to the end of there life though.
Like I said, I really think the dartyness was there before. There are long periods of time between highway trips for me. So it is hard for me to notice such things. Also it has been windy lately so that could be a contributing factor.
02 Saturn SL
for pics click the link below