No razors that are properly plated with zamak will last a long time. The problem is not the zamak but the way modern plating is done these days. You don't see the older Krona or other Zamak razors like the later model Gillettes having problems or else they wouldn't be as prevalent on the secondary market in the first place. I doubt that many lasted because they were babied.
Stainless once it starts to rot is done. It rots from the inside out. It may take a few years but eventually it will just fail like a tree that looks okay but rotted from the inside just one day just falls over. If the manufacturer doesn't do it after they cut, etch, laser, etc then the razor is most likely doomed to failure right from the get go especially once the innards start oxidizing. As an owner in your favor though is you can passivate or repassivate it and that will take care of that and stop the rotting process until the passivation layer wears off which will take a very long time. Brass depends the alloy composition also. Not all brasses are created equal and some will go through what is called dezincification.
Now back to the question at hand which is value unless the poster wasn't referring to value as in $ then the economics are straightforward. See my earlier post on why going through 4 Dollar store specials a year are more economical than buying a $40 or up razor if they can't make ten years of use before breaking down.
