A few hours after NFL owners voted to continue their standoff with the players union, the league extended its deadline for free agency by three days, putting off what threatened to become a mass purge of high-priced players from rosters. League vice president Joe Browne announced the delay Thursday afternoon, seven hours before the midnight deadline. The owners' vote after a 57-minute meeting earlier in the day had seemed to end 13 years of labor peace between the league and its union.