Usually you have the video to work with. That way you can line up edit points to any changes in the action on the video.

In BB, when you have a song loaded you can see the total run time in the upper right hand corner tool bar. You can then adjust the total measures and the tempo to get the run time you want. Account for the count in and the ending fade but you can get pretty accurate that way. Use time stretch and compression in a DAW to get it precise.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.