Hard to say.
" Average " life, probably 8-10 years.
There are many other things taking a beating.
Balljoints, swaybar bushings, etc.
When you start experiencing " squirrely handling " i.e. car is hard to keep going in a straight line, tires are wearing funny, etc. it's time to check all bushings and suspension/steering components.

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2007 C 230 Sport.