Bank of Japan board member Takehiro Sato on Wednesday warned of diminishing returns and potential drawbacks of maintaining the central bank’s massive stimulus program for too long, such as delaying government efforts to fix Japan’s tattered finances. Steady progress in restoring Japan’s fiscal health is crucial for the success of the BOJ’s quantitative and qualitative easing (QQE) campaign including a smooth exit from the huge asset-buying program, the former market economist said.