I wasn`t aware of a 256Gb memory stick, do you mean a solid state drive? As far as memory sticks go I`ve had two fail on me recently. A 4 Gb and a 16 Gb one. I only trust a tried and tested external HDD for permanent backups - memory sticks are just useful for transferring small amounts of data between machines or carrying personal data around. All of which is backed up elsewhere anyway.