當我離開該國時，我的退休居留證（KITAS）或退休居留許可（KITAP）會過期嗎？

No. The 退休 KITAS 和 退休 KITAP are multiple-entry permits, meaning you can enter and leave Indonesia as often as you want during the validity period.

Your KITAS/KITAP will 不是 expire automatically just because you travel abroad.
It only expires on its official end date, unless cancelled intentionally (e.g., through an EPO).