Don't agree with you there mate,I've never read in any owners manual that you have to brake like a loon all the time and do 100's of miles a week so your discs don't pit or rust badly,I mean if this was the case it would become a safety issue and they would have to put it in the manual as the brakes become less effective.
Surely if this was the case Renault wouldn't have changed the front ones under warranty,they would have just said'Sorry Sir your driving like puff and by the way use your car more,goodbye!'
Yes I don't do loads and loads of miles(about 7k per year) but as for braking harder,had the front discs glowing on a few occasions and cooked them which resulted in very little braking/stopping power on the road.
I've owned quite a few cars and have never known this kind of deterioration on brake discs.
Seems more likely to be poor quality kit.