CREATE TABLE table_68641 ("Year" FLOAT, "Competition" TEXT, "Location" TEXT, "Event" TEXT, "Final-Rank" FLOAT, "Final-Score" FLOAT)

Competition of u.s championships, and a Event of all around has what average year?
SELECT AVG("Year") FROM table_68641 WHERE "Competition" = 'u.s championships' AND "Event" = 'all around'
SELECT AVG("Year") FROM "table_68641" WHERE "Competition" = 'u.s championships' AND "Event" = 'all around'