However, there are cases when the duration is neither determined nor determinable.
Parties can also stipulate that their contract is concluded for an indefinite period.
What a reasonable time in advance will be will depend on circumstances such as the period of time the parties have been cooperating, the importance of their relative investments in the relationship, the time needed to find new partners, etc. More generally, it also relates to the widely recognised principle that contracts may not bind the parties eternally and that they may always opt out of such contracts provided they give notice a reasonable time in advance. Hardship requires a fundamental change of the equilibrium of the contract, and gives rise, at least in the first instance, to renegotiations. The rule in Art. 5.8 requires no special condition to be met, except that the duration of the contract be indefinite and that it permit unilateral cancellation.