If the rear doesn't sag, the struts are fine -- all the oil leaks out and then they can't hold the car up.
Accumulators seem to have a life of 6-8 years or 100,000 miles or so -- the nitrogen "leaks" through the diaphram and goes out the pump, there isn't any way I know of to prevent this. Any material flexible enough to use as a diaphram cannot be make completely non-permiable to nitrogen. Rupture of the diaphrams is rather rare, I believe.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!