Friend looking at a 1999 A6 Quattro...

Not so much- VC gaskets leak if they have 80k+ miles on the original set…not many serious issues if maintained. Ive had x2 30v 2.8 a4’s, really solid vehicles when cared for.

Just like anything, if you don’t replace/service when it’s necessary, it will add stress to another part of the vehicle which will then in turn break.