Hi --
This is a complicated and difficult topic even if we are discussing a single flash memory component. Genos has three different bulk flash memory types: the 64GB eMMC user memory, a 4GB eMMC memory for the OS and 4 x 1GB waveform memory. Each of these memories uses a different flash memory cell design and each memory has a different endurance (number of write/erase cycles).
With respect to eMMC memory, the components have built-in error detection and management: wear leveling, error correction code (ECC), bad block detection and replacement. It takes some digging to find the cell type used in a specific component. The 4GB eMMC device, for example, uses a multi-level cell (MLC) with an endurance in the 30,000 cycle range. Error management is transparent to the OS and I doubt if the OS maintains block by block cycle counts.
Waveform memory uses single-level cell (SLC) NAND flash with a 100,000 write/erase cycle endurance. Error management is the responsibility of the memory controller. I doubt if the SWP70 controller does wear leveling; it's more important to lay down samples in memory sequentially in order to read them at high speed.
Practically speaking, I sleep well at night. I certainly don't write/format waveform memory every day! Even if I did erase waveform memory 10 times a day, it would be 10,000 days until the estimated end of flash life.
I do store new voice info in bulk user memory (64GB) rather frequently when programming new voices. The memory is big and wear leveling is in play. Again, no worries.
However, do I back up all of my work? Yes.
BTW, flash drives are subject to the same endurance issues. Cheap flash drives, especially, may have low endurance. Never trust your flash drives alone. Back up flash drives to more reliable storage, too. Your time is valuable, not just the data.
Hope this helps -- pj