You can add a "Duration Calculation" item to a Playlist and it will total the length of the songs above it (until it reaches any previous "Duration Calculation" row).
This allows you to easily divide up a gig into multiple sets of specific lengths.
In order for this to work, you need to:
- Create your songs as Presets.
- Tap Actions while the Preset is selected and choose Edit Features.
- Choose Song from the Preset Type selector.
- Enter the Song Length (this should represent how long it takes to play the song live)
When you add this Preset to a Playlist, it's song length will be included in duration calculations.