If the constants are constant why do they need updating? (FAQ - Quantum)
What is evolving is our knowledge of the constants not as far as we know their values, which for the purposes of evaluation are considered constant. As technology improves ever more precise experiments give more information on the value of the constants, and this is periodically evaluated, sometimes showing previous estimates to be in error. The possibility of the underlying constants changing is a separate issue, and of fundamental importance to physics.