CREATE TABLE table_68120 ("Margin" FLOAT, "Score" CLOB, "Opponent" CLOB, "Venue" CLOB, "Year" FLOAT)

Name the average year for manly-warringah sea eagles
SELECT AVG("Year") FROM table_68120 WHERE "Opponent" = 'manly-warringah sea eagles'
SELECT AVG("Year") FROM "table_68120" WHERE "Opponent" = 'manly-warringah sea eagles'