Short answer: Usually not. Switching mid-year restarts the plan year, resets deductibles and out-of-pocket totals, and can disrupt provider relationships, so it’s generally best to change at renewal unless there’s a strong reason.
Changing carriers in the middle of a plan year is possible but rarely advisable. It zeroes out the deductible and out-of-pocket accumulators employees have already built up, may interrupt ongoing treatment if networks differ, and adds administrative work. The better practice is to shop and switch at renewal. Exceptions might include a carrier exiting the market, a major rate problem, or a network disruption; situations where staying put is worse than resetting.