[devilsgrin]

Sorcerers are unmortal beings. They live as long as they live until they are killed or will themselves out of existence. There is no evidence of a disciple of either Aldur or Torak actually 'dying'. Ctuchik destroys himself, Urvon is in Hell a play thing for the King there, Zedar is imprisoned alive, in solid rock for eternity. Belmakor and Belsambar willed themselves out of existence. No actual dying.
With this evidendce, i'd imagine Belgarion abdicating when he felt Geran was ready to be king and going off to the Vale to live until he no longer needs to. Ce'Nedra's lifespan is far more finite. Queen Xantha is a good example of age limit for a dryad, her tree is approaching 2000 if i recall correctly, and that seems to me the very upper limit of an Oak tree's life. Ce'Nedra was far more dryad than most of her ancestors among the Borunes. hence prophecy's warning to Belgarion to be prepared for lots of daughters.