Conversation so far:
What was Schroeder's relationship like with Charlie Brown in Peanuts?
For the most part, Schroeder and Charlie Brown were the best of friends, with the exception of one argument from the mid-1950s.
What was Schroeder's argument with Charlie Brown about?
Charlie Brown insulted his yellow hair and plink, plink, plink all day long [on his piano] and Schroeder countered with a barb at Charlie's coonskin cap and round head.
Did Schroeder and Charlie Brown stop being friends for a minute?

Question: How long was Schroeder on the show?
Self-contained rewrite: How long was Schroeder on the show Peanuts?