Is it permissible for acceptance of agency to be delayed after the offer?

Primary text

Acceptance of agency is permissible to occur immediately or after a delay. This is demonstrated by a situation where an agent learns he was appointed to sell something a year prior and proceeds to sell it, or says, "I accept," or performs the commanded act after a long interval. The justification lies in the fact that the acceptance by the Prophet's (PBUH) agents through their actions occurred subsequent to his appointment. Furthermore, agency is permission to act, and this permission remains valid unless revoked, thus resembling mere permissibility (Ibahah). This entire ruling is according to the school of Imam Shafi'i.