, you are now where I was a few years ago with the project 2000 S500. I replaced the entire front suspension, AIRmatic shocks and all. The difference in the car's ride was remarkable. It went from feeling like an old-school Cadillac to a comfortable European luxury sedan.
I just got through overhauling the suspension on the fiance's Honda Civic as well, last weekend. Everything except the left lower control arm is new (the left LCA was in good shape, thus didn't need replacing). Everything else is brand new, including both axles (it's a front wheel drive car). I used good parts for longevity all the way around. She and I went for a few drives in it, and I drove it to work this morning. That car now handles like it did when it was new, and it's great.
You should've seen the suspension of the S600 TT when I first looked at it. Upper control arms are not inspection items here in Virginia, but CV boots are, and lower ball joints are. The left lower ball joint must've had maybe 3mm of play in it, and the right one was almost as bad. No grease anymore, and they squeaked like several mice singing in concert. That's downright dangerous. Almost every other boot on the control arms was ripped, too, and the tie rod joints weren't tight. So, I did the whole thing to be sure. If I see a suspension problem, I look at everything. You're right, if one part is going out, then the others will soon follow. In such a case, unless I either know or can tell that a part was recently replaced, I just do everything.