To be brutally honest, modern rims are often only lighter because they use a thinner braking surface, add to that winter muck + the fact hardly anyone ever bothers cleaning their rims + pads = you can fuck a rim in mere weeks if you try hard enough.
Only rims I've ever worn out have been MTB where its not really possible to stop part way down a descent, get the file and cleaning kit out and save the rim, you just get on with it. But road bikes never worn one out but I am borderline anal about cleaning rims, even mid ride if weather is bad.
400km or 4000km??
To be brutally honest, modern rims are often only lighter because they use a thinner braking surface, add to that winter muck + the fact hardly anyone ever bothers cleaning their rims + pads = you can fuck a rim in mere weeks if you try hard enough.
Only rims I've ever worn out have been MTB where its not really possible to stop part way down a descent, get the file and cleaning kit out and save the rim, you just get on with it. But road bikes never worn one out but I am borderline anal about cleaning rims, even mid ride if weather is bad.