My solution to me getting tired of tracks in my work playlist was to keep adding more. It's currently at 2885 songs, or 5.2 days of music. It's mostly video game music, since a lot of video game music is written to not be too distracting.

Though maybe I should say the majority of the playlist consists of songs I've imported into iTunes. Apple does a decent job at letting you seamlessly integrate your personal library with stuff from their streaming catalog.