One of the guys at the office has a 1984 300D, and I recall him having all fuel lines replaced at one of the major services. I don't recall what the mileage was for sure (somewhere about 150,000 miles when he had it done), but it was recommended service. The diesel fuel begins to break down the rubber after time, and while they might not be leaking now, they very well may be soon.
You didn't state which car, but I'm assuming it is the 300SDL.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.