I believe only our age is locked post-ITA. For IELTS, it must be valid until eAPR submission. Correct me if I am wrong here.
Not only our age, all the information we provided in the profile is locked once we receive ITA. That's the reason I assume , expiration of certificates are not problem until we receive ITA.
Also, let's say my certificate will expire by the end of this week. If am creating a profile today that means am not using expired certificate to enter into the pool. Means am not fooling CIC with my IELTS details.
But if you withdraw the profile for any reason and resubmit a new profile next week, here you are using your already expired certificate, which means my profile won't be considered.
The validity of the profile should coincide with the time you create your profile.
Any members, if feel my comment are not correct are welcome to share their suggestions. It might help someone .