IMC, prestige classes are almost always based around organizations that have their own rules, benefits, and demands above and beyond what may be in the core rulebooks and splatbooks. An assassin will belong to a guild or organization of assassins who will expect its members to act in certain ways, perform certain duties and missions, and in return, gain special benefits such as access to information networks, assistance from others if necessary, etc. What it boils down to is that being a member of a Prestige Class is a big deal...it's a career choice, so to speak, and it eats up a lot of time. Dedicating yourself to two (much less three) such organizations would be impossible. In a roleplaying sense, something will have to give.
Now...you can make that a positive thing, accomplished through roleplaying, quests, and missions or you can make that a negative thing wherein you spring it on your player unexpectedly and effectively say "No, you can't be an Assassin/Peerless Archer because I don't want you to be in two groups like that."
The reason I do this is because I only have so many prestige classes in my campaign to begin with, and I take it to heart that they are more than just another class that a character could stumble into. They are linked to an organization or a certain ideal within my campaign. Overall, I think it makes for a better game. I haven't had any problems with it from my players because I ask ahead about the kind of character the player would like to have and what kinds of prestige classes or abilities he'd be interested in. From there, I give them some choices. What seems to be lost in this conversation is the art of working with a player to create a character he or she would like while also weaving that character into the campaign world and the story that's going on. DMs ask players to abide by their decisions, but I rarely hear about DMs asking for feedback, or trying to make the game enjoyable for players.
Now...you can make that a positive thing, accomplished through roleplaying, quests, and missions or you can make that a negative thing wherein you spring it on your player unexpectedly and effectively say "No, you can't be an Assassin/Peerless Archer because I don't want you to be in two groups like that."
The reason I do this is because I only have so many prestige classes in my campaign to begin with, and I take it to heart that they are more than just another class that a character could stumble into. They are linked to an organization or a certain ideal within my campaign. Overall, I think it makes for a better game. I haven't had any problems with it from my players because I ask ahead about the kind of character the player would like to have and what kinds of prestige classes or abilities he'd be interested in. From there, I give them some choices. What seems to be lost in this conversation is the art of working with a player to create a character he or she would like while also weaving that character into the campaign world and the story that's going on. DMs ask players to abide by their decisions, but I rarely hear about DMs asking for feedback, or trying to make the game enjoyable for players.