Lack of a fixed performance period does not imply that an obligation can be validly performed in every conceivable manner or at every prohibited time. The law separately regulates prayer during disliked or forbidden periods.
If a prayer obligation requires complete valid fulfilment, a performance legally defective because of its timing cannot simply be counted as equivalent to an unimpaired performance.
Two questions must remain separate:
1. No fixed deadline — the duty is not confined to one short period.
2. Validity of execution — the act still depends on other applicable conditions and impediments.
Thus, “unrestricted by time” does not eliminate the rules governing validity.