WOW... almost half a million miles!
Biggest change to suspension for most people are sway bar links... these are super neglected. Once you change all 4, the car feels so planted to the road.
Next big change is to change the springs... I feel they should be changed every 100,000 miles. Upgrading to Eibach or any reputable lowering spring kit is a huge improvement to all MB with spring suspension.
Shocks and struts are to be inspected before changing... You inspect it by taking it partially out and work the rod in and out to see if they are still strong or not. Forget about trying bounce test. Bilstein or the old Fitch (remember this brand) on the older MB are pretty much last forever...
Usual upper and lower control arms are usually changed when ball joints are worn... you can easily inspect the upper ball joint by grabbing with your fingers and bounce the car with your chest... if you feel movement, it is worn out. If it is really worn, you will hear clunk when you turn... another way to test it on your drive way... turn all the way to either side... give the car a little gas and slam on the brake... if you hear "THUCK" or "THUCK THUCK" your ball joint are worn out. Repeat for the other side.
Again, for these upper and lower control arm... it is best to change them at
100,000 miles too.
The least inspected parts are the subframe bushings... Even myself... I am not sure how to test them... but I'd suspect they are worn out by 200000 miles.
If you are handy, you can do all these stuff at very low cost. Consider the fact they only cost X amount of money... and have a lifespan of 100000 miles... I think they are damn cheap for outstanding ride quality.
It pays to use high quality parts such as Lemforder, Moog and BIlstein... they last a long time. Cheaper brands like Meyle ( I have used them) or others... they don't last long at all... as short as 12000 miles. Mileage varies depending on type of parts... but for suspension, cheap parts wear out super super fast.... waste your time and money.