I just wonder what the DO would actually gain, if he manages to break out of his prison, except for a short time being free. Even if the DO could immediately destroy all creation and maybe remake it in his own way, it seems logical that at least then the Creator would interfere and imprison the DO anew, which would start the whole cycle again.

Or do you think that the DO could actually kill or imprison the Creator on his own, if he gets free, and thus ultimately win (except if the Creator breaks free again). Doesn't seem likely, though, considering that the DO obviously couldn't prevent to be imprisoned before.

Another idea is that the DO can't kill or defeat the Creator on his own, but perhaps he might be able to achieve this, if he completely corrupts the Creator's Champion, the Dragon, to use him as a tool/weapon against the Creator (e.g. by giving the Dragon complete access to the TP). This would better explain, why the Shadow would rather have Rand on his side - and not dead - to win the ultimate victory, namely killing/imprisoning the Creator. Also Lanfear seemed to think that Rand & her could challenge the Creator with the Choedan Kal. Finally, RJ answered that it would theoretically even be possible to balefire the DO, although that this would destroy the world. Maybe the Creator could be balefired as well (one wonders, though, where he is exactly).