Well, as fate would have it, after my disappointment with my Nexus 7 and its declining flash memory performance the latest version of Jelly Bean in the form of Android 4.3 actually includes support for TRIM. This capability was lacking in prior versions of the operating system unless your rooted your device and used various lagfix solutions.
Anyway, TRIM is activated when the Nexus 7 has more than 80% battery left when off the charger (or at least 30% remaining if on the charger) and the screen is turned off for an hour which means that you should not see any performance degradation when you are using your tablet during the day. Apparently, TRIM is activated once per twenty four hours
Anyway, I upgraded my Nexus 7 to Android 4.3 yesterday after the update downloaded overnight so I will see if that makes a significant difference. What isn’t clear is if TRIM will work if the storage is encrypted (as I have not put my corporate e-mail account back on it) so I will need to do some further research prior to doing that.