Answered my own question, reference below in case anyone else needs it:
Performance Degradation Over Time, Wear, and Trim
As mentioned above, flash blocks and cells need to be erased before new bytes can be written to them. As a result, newly purchased devices (with all flash blocks pre-erased) can perform notably better at purchase time than after considerable use. While weve observed this performance degradation ourselves, we do not consider this to be a show stopper. In fact, except via benchmarking measurements, we dont expect users to notice the drop during normal use.
Of course, device manufactures and Microsoft want to maintain superior performance characteristics as best we can. One can easily imagine the better SSD manufacturers attempting to overcome the aging issues by pre-erasing blocks so the performance penalty is largely unrealized during normal use, or by maintaining a large enough spare area to store short bursts of writes. SSD drives designed for the enterprise may have as high as 50% of their space reserved in order to provide lengthy periods of high sustained write performance.
In addition to the above, Microsoft and SSD manufacturers are adopting the Trim operation. In Windows 7, if an SSD reports it supports the Trim attribute of the ATA protocols Data Set Management command, the NTFS file system will request the ATA driver to issue the new operation to the device when files are deleted and it is safe to erase the SSD pages backing the files. With this information, an SSD can plan to erase the relevant blocks opportunistically (and lazily) in the hope that subsequent writes will not require a blocking erase operation since erased pages are available for reuse.
As an added benefit, the Trim operation can help SSDs reduce wear by eliminating the need for many merge operations to occur. As an example, consider a single 128 KB SSD block that contained a 128 KB file. If the file is deleted and a Trim operation is requested, then the SSD can avoid having to mix bytes from the SSD block with any other bytes that are subsequently written to that block. This reduces wear.
Windows 7 requests the Trim operation for more than just file delete operations. The Trim operation is fully integrated with partition- and volume-level commands like Format and Delete, with file system commands relating to truncate and compression, and with the System Restore (aka Volume Snapshot) feature.