What is the minimum length a shot needs to be in order to synchronize in a multicam?

I had 5 cameras for a concert, and one camera person kept stopping every few seconds (had to manually sync up his shots). In the future, I want to ask him to keep shooting ... but I'm not sure how long to ask him to shoot for. Is it 30 seconds, or one minute to assure synchronizing. I am shooting classical music, so the sound is very consistent for each camera.

ruth.antrich wrote: … one camera person kept stopping every few seconds (had to manually sync up his shots). … I'm not sure how long to ask him to shoot for. ….

There's no minimum, could be a single frame.
And there's no need to manually synch:

Find in all 5 angles in use a synch-point - lights go on, a BOOM of a drum, a flash of some ignorant in the audience, a referees whistle (oops, that's what I'm using…)
Set a single Marker in each Angle.
In the MC making dialogue, use Synch 'On first Marker' (= in terms of: Marker can be anywhere, even at the very end, when all clap) and Ordering 'Content Created' (=that cares for pause/rec orphans)



=> then, a cam angle with hundreds of strayed short clips will be synched.

Thanks for that info! I have been struggling with this too!