Southwest Airlines Rapid Rewards points never expire as long as your account is open and in good standing.
Previously, Southwest points would expire after 24 months of inactivity, so this is a nice improvement over the old policy.
However, you should regularly redeem your Southwest points just in case they are devalued.
Comparison of U.S. Airlines' Policies
Below are the mileage expiration policies for every major U.S. airline.
