What are the read/write life cycles for flash memory?
Depends on the type of memory. IIRC, NAND Flash (the kind used in solid state drives) has 1 million read/write cycles before the memory block becomes unusable. 1 million sounds extremely low, but SSDs have read/write controllers that distribute the load across all of the memory blocks. The net result is that an SSD will have a longer practical lifespan than the average 5 year life of magnetic platter hard drives.
Basically, if you don’t use the Flash card all that much—let’s say you want to archive documents for long-term posterity as part of an archival storage project—the data will be preserved for many, many, many years. Much longer than it would be preserved on a standard magnetic platter hard drive or on an optical disc.