Most consumer hard disks will last about 5 years.
Flash drives last according to usage. The numbers have changed since I last looked into it, but FLASH was good for about 100,000 erase cycles before they warranty was out. We ran continuous tests and found it far exceeded that so they were being conservative. Sandisk gave it 300,000 erasures with their controller. That's some 1,000 writes a day for a year and far in excess of normal usage. As such, there is no exact amount of years I can tell you such will last.
IE: the Compusa 1 Gb for $59. Size wise suitable for my needs, but how do they compare to flash drives..Lots less $$ per MB of storage...