Ideally, the "level cap" your game systems should be capable of supporting should always go noticeably ABOVE what your players would be able to achieve with a "completionist run" (excluding console cheats and the like, obviously).
Meaning: if by the end of the game the player's party has a good chance to be anywhere between level 11 and 13, you should cap your system at 15 or above.
The idea of having your player hitting the level cap WAY before being through the content of the game is fairly bad.
P.S. For context, this IS something that could happen in BG1... And maybe in BG2 before the Throne of Bhaal expansion, too?
Not sure. I basically played it without ToB just once when it was a fresh release so I can't really remember.
