I find this thread odd. My RK-9000 caps show no signs of wear, then again I have only had the keyboard for a few months now.
I think everyone's experience is going to differ slightly, there are too many factors when it comes to wear. How much average oil production in the fingers, how acidic it is, how good the owner is at keeping their hands clean, and how obsessive they are about over-cleaning things.
But from a non-anecdotal technical standpoint they should wear on average as fast as any Lasered. key.
Also when it comes to anecdote online people are much more likely to post about their problems with something than to post about their satisfaction with it.
By the way, I sent myself into a probably obsessive-compulsive re-evaluation of my keyboard dilemma after seeing that the Filcos are back at PChome and reading more about the Das. But despite this I still pulled the trigger on the Rosewill today. I simply feel at the price point, convenience, and what I am looking for in a keyboard it meets all of my needs and delivers them at the best price and convenience to me.