Thanks for the Question, It has a Very Simple Answer but Please Read the
Elaboration
The CES (Corrective Exercise Specialist) and PES (Performance Enhancement
Specialist) are not certifications they are considered "Advanced Specializations
by the NASM.
I'm not sure how they differentiate this classification but to answer your
question there is no expiration for the "advanced specializations" with the NASM.
Just because they do not expire it is not recommended you purchase them
immediately just get another certification or even to learn the tons of
information which they give you.
NASM-CES and NASM-PES Count as Continuing Education
Units/Credits
Both CES and PES count for CEUs (Continuing Education Credits/Units) for most
major personal trainer certifications including the NASM CPT (Certified Personal
Trianer)!
For the NASM-CPT both advanced specializations count for 1.9 CEUs which along
with your CPR cert will give you all the continuing education you need to keep
your CPT certification current.
If you just got the CPT you should only get one advanced specialization
which would re-certify your CPT certification which expires in two years.
After the 2 years are up, get the other one and you can re-certify for the next
two years.
Take your Time with the CES and PES Courses
If you are very interested in learning more about exercise science,
flexibility and performance enhancement it is worth it to take your time with
the online interactive courses the NASM offers for the PES and the CES.
There is a lot of information to digest and it is better to take a slow
approach and learn everything thoroughly rather than just cramming all the
information in your head for the short term so you can pass the tests.
If you're currently training clients taking your time with the PES and CES
course material will allow you to implement some of the new concepts you learn
on your current clients and practical experience is far superior to anything in
a book or even in a video presentation.