John Smoltz is expected to sign with Boston soon. This means that after being on Atlanta's big league roster for 21 seasons (although just playing in 20 seasons as he missed the 2000 season with an injury), Smoltz will likely finish his career in a Boston uniform.
Henry Aaron played in 21 seasons for the Braves (1954-1974) before playing his final two seasons for the Brewers.
Warren Spahn played for 20 seasons for the Braves (1942, 1946-1964) before playing his final season for the Mets and Giants.
Among players for other franchises, Ty Cobb played 22 seasons for the Tigers before playing his final two for the Athletics. Willie Mays played 21 seasons for the Giants before moving on to the Mets. Mays and Spahn both missed time because of military service.
The most seasons any pitcher had who pitched for the Braves and no other franchise is nine seasons by Rick Camp. The longest-tenured Braves "lifer" is Chipper Jones who will be playing his 16th season for the Braves in 2009.