The following is based on personal experience. In addition to durability I think it is important to look at how a company takes care of those who have issues. If 98% of a companies skis are bomb proof but they refuse to take care of the remaining 2%, than that is an issue. I would rather buy from a company that has 10% warranty rate, but bends over backwards to help their customers, rather than looks for excuses on why it was the skiers fault. This also asks for a bit more discretion and honesty on behalf of the shop employees and customers. I have seen a pair of skis get brought it for warranty, that had been driven over. The customer had been skiing in low coverage and ripped a large section of base out of the skis, rather than pay for repair, he drove over them, IOT try and warranty them. I called him on it, and ended up selling him a new pair of skis. I also knew a shop tech who would work on burton boards IOT make them look like a warranty issue. These actions undermine all of our integrity, and encourage companies to be sticklers on warranty issues. The same can be said when it comes to hitting rails. The idea that a ski should be able to take getting slammed into a cold iron/steel bar 100s of times a day without damage is ridiculous. Any ski that can take that will either ski like shit, cost a fortune, or be a work of god.
Returning to the main topic of the thread, here are a list of brands that have impressed me with their skis' durability and longitivity. Keep in mind I do not ski rails, but have been known to hit a rock or two, and don't go out oft way to maintain my skis. I do expect my skis to take abuse all season and still ski the same (re: flex pattern) for a couple years at a minumum.
ON3P skis, these have the strongest bases and edges of any ski I have used. I have not had a single core shot or significant edge damage in the last 4 years I have been on them.
Dynastar; I think dynastar makes some of the best damn skis out there. I had both the XXL and Big Trouble for several years, and they skied the same on day 150 as day 1. The flex pattern did not change, but maintained constant for the three seasons I had them. The bases on the big troubles were bullet proof too. They got scratched a bunch, but never more than a few tenths of a mm deep, and no core shots of any kind.
Blizzard; absolutely no problems of any kind.