What is the average year needed by a user with uber fans to become an elite user?
AVG(user_yelping_since_year) where user_fans = 'uber';
SELECT CAST(SUM(T2.year_id - T1.user_yelping_since_year) AS REAL) / COUNT(T1.user_id) FROM Users AS T1 INNER JOIN Elite AS T2 ON T1.user_id = T2.user_id WHERE T1.user_fans = 'Uber'