If we're talking about lifting, It's better to switch your routine after a while to avoid "plateauing", but not so often as to not be able to track progress and perfect form in lifts.
This is one of those 'true but' statements. I think it's actively harmful to provide it to beginners who don't have the context to understand what that means. Vanishingly few beginners are running a routine long enough or hard enough to suffer from this problem.
