You must be joking. We would be in deep trouble if flash memory held its information for only about a year.
Nope, not joking. It also depends on the process size. Nice big (i.e. low capacity in a large die size) SLC flash cells hold data for quite a long time. The higher-density they get (and the less electrons per bit used to store data) the worse it gets.
So a lot of device firmwares and BIOSes, which generally use nice big chunky flash cells, will last 10-20 years. High-capacity flash storage, not so much.
That's just the way it is. Flash is currently the least worst solid state storage solution we have, but it still sucks.
(Note that if your device is powered on occasionally the flash can error-check and rewrite itself, which at least partially "resets" the time for data loss. This is only an issue for devices that are constantly powered off or devices that will not rewrite themselves as required.)