The PAL only needs to be valid when you submit your complete study permit application to IRCC. The PAL does not need to be valid when you travel to Canada or when you begin your program.
For example: if an applicant starts in May 2026, they can apply with a PAL issued in 2025, as long as the complete study permit application is received by IRCC before Dec 31, 2025. Applications must be submitted before 11:59pm EST on December 31, 2025, in order for their PAL to be valid, and IRCC considers applications based on Coordinated Universal Time (UTC) 11:59pm, not local time zones, so applicants should not apply at the last minute and should submit their study permit application at least a day before December 31.