How often and for how long does Trim Enabler need to run?
What I used to do was enable TRIM, reboot, create and delete an encrypted disk image that almost filled the free space, leave my MBP idling overnight, disable TRIM, and reboot. That restored performance.

I'm not sure r/w volumes will tell you anything useful. The OS reuses erased blocks and the current controllers garbage collection is supposed to make TRIM largely irrelevant (or at least that's what I read).

I don't have that machine anymore and it seems like a lot riskier process under 10.10 so I'm not doing anything with TRIM on my Mac Mini w/ a Samsung 840 EVO.