Clauses About Duration of Grant
Sometimes, the time line may be more complicated: the grant of exclusive rights may last for a limited period, but the other party's retention of non exclusive rights after that period may last for the full duration of the copyright.
While commonly so, assignments of rights need not be forever (“forever” meaning the duration of the copyright term). (Other ways of saying “forever” include “perpetual,” “irrevocable”) Some contracts take exclusive rights for a period of time (for example, one year) and then allow the rights to revert to the author. Sometimes, the time line may be more complicated: the grant of exclusive rights may last for a limited period, but the other party's retention of non exclusive rights after that period may last for the full duration of the copyright.