cabanalane

Just wondering have anyone of you heard or experience spring sag with lowering springs? Or do they typically last a life time of the car? In my random search on the web, there's also talk about progressive rate springs sagging? Is it fair to say that all springs, including OEM will sag?

The specific brand I'm looking at is Eibach Pro-Kit.

Lastly, there's been threads about fake Tein knockoff springs. Is Tein a good brand that there would be knockoff springs. I'm not found any info someone try to make knockoff Pro-Kit springs or springs from other brands.