Do prestige classes curb creativity?

[Storm Raven]

Then it depends on your campaign.

Do you have PCs progress past 20th level? Then make the rule to be no more Total PrCl levels than Base/Core class Levels.

If not, then introduce the concept of "Unlearning."- abandoning one PrCL for another. The PC gives up the bennies of the PrCl he's abandoning to learn the new path. Once done, the PC can NEVER regain acceptance into the PrCl he has abandoned.

OR you can simply do what the flavor text says for a lot of PrCLs...there are all kinds of organizations with PrCl's, but not all people in the organization have the PrCl. So that Ftr10/Dervish10 can be a Harper, he just can't have Harper PrCl levels.

Here's what I do: subject to approval (i.e. I review proposed PrCs that I'm not familiar with before I allow them in the campaign), characters can take levels in any PrC they qualify for. The PrC may be attached to a particular organization or it may not. If it is, members of that organization may have opinions on other professions, or they may not. If players want to mix and match PrCs, they can, to any extent they desire to do so.

Thus far, there have been no practical problems with this approach.