Conversation so far:
How old was Stan Kenton when Stan Kenton started Stan Kenton's career?
In April 1936.
Was he immediately successful?
CANNOTANSWER.
Where did he begin his career?
CANNOTANSWER.
What did he start out doing in his career?
Gus Arnheim was reorganizing his band into the style of Benny Goodman's groups and Kenton was to take the piano chair.

Question: How long did he stay with Gus Arnheim?
Self-contained rewrite: How long did Stan Kenton stay with Gus Arnheim?