You can "forget" about CCSA certification expiry and only focus on your current highest certification, CCSE.
If you pass a Specialist exam before your CCSE certification expires then your CCSE will be valid for one more year (to March 2026).
You can then target another Specialist exam and passing that second exam will give you CCSM, which will be valid from two years from the day you pass that second Specialist exam .
CCSM would then be your current highest certification, and the one that you would want to extend (to three years total), by passing a third Specialist exam.
Passing a fourth Specialist exam would award you the CCSM Elite, which would then be your current highest certification.
The pattern ends there and from then on you simply use Specialist exams to keep the CCSM-E valid, extending the certification one year at a time per Specialist exam.