>> It also wouldn't win you any significant increase unusable lifespan, because when your drive starts retiring large numbers of blocks, all of your blocks are on the verge of failure.
That's not true. Blocks degrade when written to. Most files are written once and read many times.
You're forgetting that SSDs use virtual addressing so writes are distributed relatively equally over the whole drive. Even data that is written once and never changed logically will probably move around on the SSD due to garbage collection. The virtualization algorithms are kept relatively secret, but I assume good SSDs will move full unchanged blocks around occasionally to distribute write load more equally on the physical blocks.
Yep, wear leveling actually works. On some SSDs, there are SMART indicators to tell you the average, max and min block erase counts, so you can see for yourself that the erase counts are all about the same across the entire drive.
>> I assume good SSDs will move full unchanged blocks around occasionally to distribute write load more equally on the physical blocks.
I hadn't considered that. Make sense. Better to move never-changing data to blocks that are still good but not worn out so those available writes can be utilized.
That's not true. Blocks degrade when written to. Most files are written once and read many times.