Lanefan
Victoria Rules
Once they've met that technique, though, it becomes a known thing in the setting (and one might sometimes ask, quite reasonably, how and why it wasn't known before, depending on how it's introduced) and thus theoretically a player's next character might have undergone said years of training and learned that technique.Why? Why can’t there be things in the world the players do not know about until they meet it, that would require years of training under a master of that technique in order to be able to do?
For example if the PCs go up against the Monks of Kai Shan (who are all Human) and those Monks have cool fighting abilities never seen before, even if the Kai Shan Monks were previously completely isolated from the outside world (unlikely). their secrets are out now; never mind a player might want to have her next character be a Kai Shan Monk.
So, sure, you get to surprise the PCs once. But after that, whatever you surprised them with becomes part of the setting. Kind of like introducing a brand new spell to the setting.