(Scroll down to answer from "Jon" of Micron)
ANY UNUSED SPACE is used to manage garbage collection and wear leveling. It doesn't matter if it's unpartitioned space or if is it is simply unused within the partition.
(typo correction mine)
So, for all intents and purposes, I can leave it alone, and, if I ever use up the 222 GB of "C:", I can create another drive in the unallocated space to move a few apps (programs) into, esp. if such would do many writes to the folder or drive it is in.
For all practical purposes, this drive should easily outlive me. Maybe my daughter, too. Although, that begs another question:
Does reading data on a SSD or USB flash drive "refresh" it?
Some things to look out for is make sure you do not automatically defrag all the time and use Trim. You must set it up with the OS with AHCI for the fastest speed. You can't change it after the OS is installed.
If you use it for a Plex server, transcoding should be done on a ramdrive. That is very read/write intense. Everything else is just normal wear and tear.
Let's just say you keep the 222 gig as your Boot drive and it starts getting errors. There is no guarantee you can format your empty space and use it for a boot drive. Boot sections can only go on certain sectors of the drive.