InfoPath Dev

At my work we have multiple buildings that often get used in different forms that i create. These buildings are in a list dropdown. We are adding a new building and getting rid of another. I can add the new building to the list easily enough, but how can i keep the old building, but not allow users to select it after a certain date? I don't just want to delete if from the list because it may cause issues with previously submitted forms.

Are you using Get choices from an external data source (If this is a list in SharePoint)?, If so, create a new column like Building Status. Give it values of Active and Inactive (or something similar). Now, on your form, add a filter to this connection and filter by Active.