Back to Steel. I rather like the stuff. For the most part it is strong, malleble, ductile stuff. Properly prepped when new I believe it can exceed 30 years without major refinising if appropriate care is applied. Special interests of maintenence will included electrolisys prevention, and interior plumbing. Small plumbing leaks can become big problems as water (both fresh and salt) will collect along seams of frames and rust the hull from the inside out.
If you are purchacing used see how much access one can gain to the inside of the hull to inspect any area where water can collect. It's pretty easy to see the exterior condition when hauled. Areas that cant be poked and prodded or seen very well inside should have a lot of ultrasound attention by way of those spots.
A nice thing about steel is a good welding shop can be found in even the less industrial areas of the world, and reasonable repairs be affected. Maintainence must be done quickly and responsibly. Schatches digs dents sould have their coatings attended to at first opportunity.
Hope this helps.