How long should rotors last? LAC

[tihol_tiholov at sd27.bc.ca]

Well, the title explains it all!  The reason I ask: my parents 97 A6 Avant
>It just seems to me that the rotors should at least last as long as a set
>of pads...the pads still have about 5mm of material on them!

That's what I thought, too, but no cigar.  Experience on a New Beetle with
plenty of highway driving:
1. Rear rotors (solid 9 mm new, 7 mm min thickness) warped at under 80K km,
pads were at least 70 % left.
2. Front rotors are still 2 mm above min thickness with pads at least 60 %
left - now the car has about 170K km.  I'll have to replace these soon, but
not necessarily the pads.
I attribute this to Piech (Porsche) design - aggressive pads and need to
brake from higher speeds in Germany.

Greetings,
Tihol