CREATE TABLE table_203_589 (id DECIMAL, "protein" TEXT, "natural host" TEXT, "normal function" TEXT, "prion state" TEXT, "prion phenotype" TEXT, "year identified" DECIMAL)

how long after the third prion characterization would it take for another to be characterized ?
SELECT (SELECT "year identified" FROM table_203_589 WHERE id = 3 + 1) - (SELECT "year identified" FROM table_203_589 WHERE id = 3)
SELECT (SELECT "year identified" FROM "table_203_589" WHERE "id" = 4) - (SELECT "year identified" FROM "table_203_589" WHERE "id" = 3)