Services
(1) The President appoints the UPSC/Joint Commission's Chairman and members; the Governor appoints a State Commission's - with roughly half of every Commission's members required to have at least 10 years' prior Union/State government service. (1A) A vacancy or absence in the Chairman's role is temporarily filled by another member the President/Governor appoints. (2) Members serve a 6-year term, or until age 65 (UPSC) / 62 (State/Joint Commission), whichever comes first - they can resign, or be removed under Article 317. (3) A member cannot be reappointed to that office after their term ends.
This ensures Public Service Commissions have both experienced government insiders (the roughly-half rule) and a defined, protected term of office - and the one-time-only rule (no reappointment to the same Commission) helps ensure members don't feel pressure to please the appointing government in hopes of a renewal.
This is why a UPSC member typically serves a single six-year term (or until age 65) without any possibility of reappointment to that same Commission afterward - a structural safeguard against members currying favour with the government for a second term.