My parents in January 2023 received their visitor visa, however, they are not able to come to Canada before September or October of 2023. Is there any rule of making the first entry within a certain period of time e.g., within 3 or 6 months from the date of issuance or it doesn't matter, and they can enter anytime during the validity of the visa? I couldn't find any related rules or guidelines on IRCC. Could someone please help and share their experience? Thank you.