In short: it's marketing trick.
It's meaning is that Genius (KB maker), states that the keycaps can withstand multiple key presses continuously on longer periods of time. E.g if you use KB intensively.
"Durable keycaps, born for high-intensity users."
source:
http://us.geniusnet.com/product/slimstar-130
Though, any KB keycap is basically "born for high-intensity users" since they are made from strong plastic. In the other hand, key switch is something that can break and when that happes, that key no longer works, despite it's keycap being made for "high-intensity users".