Hope the title is not misleading, as rather than offer any information I am here for advice.

My 2003, S-Type 4.2 just turned 100k. The shocks and struts are originals. I have it 4-wheel aligned every 10k, so the suspension parts are consistently inspected and rear arms did need replaced recently.

There are no visible leaks.
The quality of ride is still great.
There is no nose dive when breaking at any speed.
There is no squat when I punch the accelerator at dead stop.
I may have a slight sense of body roll, but I think that it may be from leaving Perelli's and going to Hankook's (which I will not do again).

My primary question is do I change because common sense says that nothing lasts for 12 or 13 model years and 100k (other than the spark plugs) or should I perform preventative maintenance?

The secondary question, assuming that new equipment is performed, is to what?

As I research I am finding a variety of firmnesses and rides types. One parts store says that there is some tag indicator on the vehicle somewhere to indicate what factory spec was. Another says that is bunk and to decide what type of ride quality I want and then go with it.

To say I am a bit confused would minimize the situation.

 

If there is no deterioration in ride quality, why change them?

There's many many things that last more than 100K miles on a car. It's not a magic threshold.

 

Hard to say?


I have 122K on my original CATS struts and they still ride fine. Do look for oil on the tubes which indicates the seals have started leaking.
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Based upon what you've said, I wouldn't change the shocks either. Especially if your tires continue to wear evenly across the tread....

My 2005 S-Type 3.0 is approaching 93,000 miles and still rides comfortably with dead-even treadwear across all four corners. Until something deteriorates, I'm sticking with my factory shocks....

But I did notice during my last oil & filter change / tire rotation in late July that both of my rear anti-sway bar links were shot. So I ordered a pair of new ones from Welsh Enterprises for about $60 total. They definitely improved the feel of the rear end of the car, and the rear end no longer sporadically "clunks" when backing down my driveway. You may want to check yours if you haven't done so lately....

 

I would parrot the advice given; don't change shocks if you like the ride and they are not leaking.

However, if you do decide to change them and decide to DIY here are two head up:
1. knuckle will need to be disconnected at the upper ball joint to give clearance to pull out the front shock/spring assembly
2. do not use two J-hook type spring compressor to compress the spring during shock removal. Use one-sided cast arm spring compressor to evenly compress the spring and not impart any lateral loads to the shocks.