The recommended way for safe simulations is that you will never change the Eclis version used by a given simulation.
On the other hand, when designing a new simulation, you generally can move to a newer Eclis version because it will bring fixes, and also because Eclis devlopers work hard at providing upward compatibility
However, there are a few occurrences of broken upward compatibility, which can imply that the user changes some parts of his usual parameter files when changing Eclis (...)