We add a task action to alert us in the future when the solicit code should be remove/reevaluated. We don't have many though, it's very case by case. I can see that being more troublesome for anyone who uses temporary solicit codes often. Curious to see the other responses.
Yes, I agree with both Traci and Amanda. We use a "Temporary Solicit Hold" solicit code for our new alumni (new grads), as we do not solicit new grads during the first full year after they have graduated. You can use an action alert to follow up to remove the code. In our case, since this only applies to alumni, our documentation for importing new grad info includes the procedure for adding the solicit code (as well as a Solicit Code Explanation in Notes), and the procedure for removing the code every year after graduation. You can accomplish all of this with a combination of global change and import.