Elections
Notwithstanding the foregoing provisions of this Part: (a) SC/ST reservation in the Lok Sabha and State Assemblies ceases after 80 years from the Constitution's commencement; (b) Anglo-Indian nominated representation ceased after 70 years - though in both cases, existing representation continues until the sitting House/Assembly is dissolved.
This is the "sunset clause" setting the actual expiry timeline for the reservations described in Articles 330/332 (SC/ST) and 331/333 (Anglo-Indian) - repeatedly extended over the decades by successive amendments (originally just 10 years in 1950, now 80 years for SC/ST reservation, meaning it runs until January 2030) for SC/ST reservation, while the Anglo-Indian nomination provision's 70-year clock was allowed to lapse in January 2020 without further extension.
This is why SC/ST reservation in Parliament and state assemblies isn't a permanent constitutional feature by original design - it's periodically renewed by amendment, currently extended to January 2030, at which point Parliament would need to pass another amendment to extend it further or let it lapse.