Who, in a live situation, actually has time to preview the end of the current track playing. In all the years that I have played I have rarely ever had time to be testing out exit points in a track. An experienced DJ just knows when they are as 99% of all dance-floor tracks are written to a formula. It is with this formula, the intro, body and outro that DJs use to program their mix. The only time you might add "cue points" is at home while previewing your tracks. I can't see "sandboxing" being widely used by the professional DJ
