I have no hard evidence for the 1K figure I had been told.

What I learned when studying this years ago is that flash cells have an endurance of more like around 10k writes, though I'm sure with the advancement of the technology that's increased* (I've head figures of up to 1M writes). Conversely, the wide spread of flash technology also means that there will probably be companies producing cheap, lower-quality flash, with less write cycles.

* I went on DigiKey and picked a few current NAND Flash ICs at random, from different manufacturers (PDFs: 1, 2, 3) and each of them specifies an endurance of 100K Program/Erase cycles and data retention of 10 years.