Let's say a concert promoter hires a video production company to record their concerts with the agreement that the video copyright goes to the concert promoter.
If this happens once in a while, they can just sign the agreement each time there is a concert.
What if this is an on-going business, meaning many concerts are held throughout the years, can they sign some sort of perpetual agreement that would make it unnecessary to sign one every time?
12345 video production company agree to give all copyright to 54321 concert promoter for all the videos shot at their concerts from now on .
Obviously if the video company changes their mind later on, they can request a new agreement to void this one.