Several variables are at play. First, regarding plating: Rhodium- expensive, long wearing Gold- expensive, significantly softer than Rhodium or nickel Silver- cheaper, significantly softer than Rhodium or nickel, may last a bit longer than gold because it is cost-effective to lay a heavier coating. Nickel- cheaper, surface-hardness is comparable to Gold/Silver, but is thicker and just slightly more soft(in the sense that its surface will give, rather than scratch off or crack), giving it more "flex". Chrome- cheap, hard. Not as forgiving of scratches/dings as other finishes, but with care, is easily more durable than the others, barring Rhodium. Nickel's life may be extended/diminished by handling, beard coarseness, exposure to cleaning agents, water composition, extended exposure to water in conjunction with soap, steel, various elements. If you don't routinely drop your razor, don't leave it sitting with shaving goop & water in/on it, and if you don't use harsh cleaners on/around it, yes, it should last your lifetime. For something to pass on to a couple or three reasonably careful generations, my inclination would be Rhodium.
If the plating was done properly, nickel over brass is pretty tough and could hold up for decades. BRW's were done fairly well so will probably stand the test of time. Wiping the shaver down after use could also help add to plating longevity...
All of the above. If you ensure that the razor is clean, in particular no build up of crud in the corners and hinges etc, it should last several lifetimes. I prefer nickel or chrome plating over gold. The latter seems to collect stains and crud more easily. Or maybe it shows more. Don't know. But the gold plated razors I've got seem to need cleaning a lot more often than the others.
