I don't sell much, but I am involved in the occasional gallery show and have sold some work. I personally don't know that the buyer cares that much but I care a great deal, so I use fiber paper. I am actually using it more for the reason that it creates the look I am after, but I appreciate the fact that I can say that the prints I make are about as archival as gelatin silver prints can be. There is a level of professionalism that is communicated when you can say that. While I would not be surprised to hear that good RC prints will last a very long time, I don't imagine that they are as good as fiber.