I use RK9000s exclusively on my desktops, and I can type all day on my MBP without pain. But I do notice that on the MBP I type differently, because key travel and activation force are so much less than the MX Blue switches I'm used to. If I used that kind of force on an MBP keyboard, with nothing really to backstop it, I'd expect to get sore pretty fast, just as I would if I used the same kind of force on MX Blues that I'd need to activate the switches on one of my old Model M finger-breakers.

Typing comfortably on an MBP I think needs a somewhat different approach. It feels less like typing than like drumming my fingers on a table, which never quite all the way stops being weird. But it works, and as I said, I can do it all day without getting sore. Perhaps you can, too!