Just when should you replace the shocks on a 275K 300D?

[Carrameow]

Just when should you replace the shocks on a 275K 300D?
I got itchy hands and was out working on my car the other night trying to change my shocks on my 275,000 mile 300D. When I got the old ones of, I found out to my surprise that hey were still gas charged.
The fact that they were still gas charged and the fact hat the car rides smooth tolme to leave them in.
My other benz, a 240D with 225,000 miles has good shocks, too

How do I know hwn the shocks are bad?

Credentials:
http://mywebpages.comcast.net/rtc9/BENZ.html