Il mio KITAS o KITAP per pensionati scade quando lascio il Paese?

No. The KITAS di pensionamento e Pensionamento 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 non expire automatically just because you travel abroad.
It only expires on its official end date, unless cancelled intentionally (e.g., through an EPO).