What is the latest year that 6th, Heartland is regular season?
CREATE TABLE "year_by_year" (
  "year" real,
  "division" real,
  "league" text,
  "regular_season" text,
  "playoffs" text,
  "open_cup" text
);
SELECT MAX("year") FROM "year_by_year" WHERE "regular_season"='6th, Heartland';