from my experience with SS lines (Troutman, DOT approved) I'd do it again:
1986 190D 2.5 lines were on for over 200K miles (sold).
1987 300E have about 150K miles on them so far.
1979 6.9, about 10k miles over 18 years so far.
Note that the fluid is flushed about every 2 years.

__________________
Hanno
'79 6.9 Sold (after 27 years)
'83 280SL, 5 spd.
'94 E320 Sdn. 5 spd conversion
'02 E320 Sdn.(on loan to mom!)
'87 300E (5 spd. conversion) Sold
'05 E500 Wagon