The term evergreen is known from botany as plants staying green all year and from music as songs not just being a hit for a few months but capable of generating royalties for years and years.
Data should also stay evergreen. I am a believer in the “first time right” principle as explained in the post instant Single Customer View. However, you must also keep your data quality fresh as examined in the post Ongoing Data Maintenance.
If we look at customer, or rather party, Master Data Management (MDM) it is much about real world alignment. In party master data management you describe entities as persons and legal entities in the real world and you should have descriptions that reflect the current state (and sometimes historical states) of these entities. Some reflections will be The Relocation Event. And as even evergreen trees go away, and “My Way” hopefully will go away someday, you also must be able to perform Undertaking in MDM.
With product MDM it is much about data being fit for multiple future purposes of use as reported in the post Customer Friendly Product Master Data.
Liliendahl on Data Quality 