My understanding is that TRIM just tells the SSD to go clear out cells marked for "deletion". Deleting a file on an SSD doesn't guarantee it will actually by physically deleted. It might increase the wear level a bit, and if it TRIMs when you're busy, it might impact performance for a bit. I think windows tries to TRIM only when the SSD isn't busy, so if you've had a lot of torrents running, it might never have gotten to the point where it triggered the TRIM to run.