Steel fatigues over time as well. My old touring bike, which I had for 23 years, eventually started to feel too whippy for comfort. And I've seen steel frames break - usually track frames, while some large and muscular sprinter is starting off the line for a kilo. There is no perfect material that lasts forever.
As to a do-everything bike, I vote for cyclocross bikes as well. My husband loves his Ridley Crossbow, and he has no intention of riding 'cross, ever. It gets ridden with touring tires to do the bulk of his riding. The carbon road bike comes out only occasionally. I bought a steel touring bike 2 years ago, but now I'm thinking that it's a waste for someone who doesn't tour, much heavier and more sluggish than his Crossbow. I'm thinking of selling it to buy something like the Ridley, perhaps a Kona Major Jake.