Unlike the CASA Part 66 “Module” Exams, there is no legislated time limit window on when a “CASA Basics” exam must be applied to a licence. Hence, the “basics” never expire.
See the FAQ What exactly is the “Ten Year Expiry” on my CASA Module Examinations?
Furthermore, they can be used to provide credit towards CASA Part 66 examinations.
See the FAQ What good are my Basics Results?