Ian,
Some more info on CMP can be found here and there are some commands to see if there are any virtuals that have CMP disabled. - https://support.f5.com/csp/article/K7751
When traffic increases, you will likely see an impact from additional SSL and compression being done on the platform. If there is not a compression or enterprise license on the older platform then the Compression is likely not being done in the chips designed for that, so that is eating CPU cycles.
Also SSL is moving to more modern ciphers which the older platforms cannot do in hardware, so it may not matter if you have an advanced SSL throughput license that would unlock the SSL Hardware on the platform.
If your system is still under a valid support contract, please consider upgrading as this code base is approaching its sixth birthday and is no longer supported. EOTS(End of Technical Support) for 10.2.4 was 31 Dec 2016.
To see what versions of code are compatible with your platform check out this article and try to get to a version that still has some time on the support clock - https://support.f5.com/csp/article/K9412
If you have never done an upgrade before, or even if you have, I encourage all to read this document that covers the upgrade procedure. - https://support.f5.com/csp/article/K84554955
HTH,
Carl B.