The answer is not straightforward. For instance, it partly depends on the climate. I owned a 1971 Travco which, up until 2005 had the original brake fluid in it. Now, it spent its whole life in Colorado which has an extremely dry climate. It would not have lasted that long in a humid environment.
If the brake fluid you bled out did not look too bad, I'd let it go. But I'm in Colorado. If it looked bad, and I lived in Alabama, I'd do the clutch system.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13