My understanding of TRIM differs from yours. It is my understanding that TRIM impacts write operation performance, not lifespan. However, SSD onboard electronics may include "garbage collection" services that may reduce lifespan [1].
NAND memories require a delete operation of already written sectors before a new write operation can be executed. The TRIM commands shift this delete operation to a time other than during the write operation.
TRIM commands can be issued by filesystem drivers, such as during file deletions or during filesystem formmatting, or by user command such as with the Linux
fstrim.
[1]
http://en.wikipedia.org/wiki/Trim_%28computing%29