Would you, personally, go by your own feel for how suspension is performing or by mileage?
Neither. I remove all 4 dampers every 20K miles or 18 months, whichever comes first, and send them to a shock dynamometer in New Zealand. It's pricy but I need to stay atop my ride's ride. You see, I deliver eggs to eco-conscious chefs who eschew cartons in the name of lessening trash. Darn hippies.
I'm so glad J_R hit your G-spot.
I know a bunch of "housewives" who wouldn't let you near theirs' now.
SERIOUSLY: (which means the above was in the name of humor-desperately needed in this thread)
When I recently scoped out a 2000 MGM with 100K, I expected our friend to buy it.
It wallowed as everyone would expect and I was sooooooooo looking forward to replacing the 4 shocks; yes, no front struts.
"What exactly caused the feeling of wollowiness I felt?", you ask?
The age, the miles, the feel and the track record of all the bulbous American land yachts which came before and after it,
All of the above.
Dampers are so affordable, people needn't know the specifics of aging to spent time and money smartly.
Much like my engine's oil's lifespan determination, one or two UOA's established the usability of my owner's manual's recommendations.
In my experience, suggested OCI's are saner than 50K-blanket damper change-out sales pitches.
PERSONAL: The long absence of the "$200 car-for-sale-down-the-street" means my G spot is vestagal.