Archiving Photos - USB, DVD, something else?

I currently copy a DVD of original images (JPG) every time I make a physical photo album - and place the DVD in the album.

I'm considering moving to very small USB sticks because they are smaller, easier to manage, and have a better medium-term future (USB 3 slots will be USB 2 compatible whereas most computers in about a year look like they won't even have any optical drives anymore).

Has anybody seen studies that examine the use of USB (Flash) storage for archiving - and if there are some technologies that are better suited to the task than others? Any other advice?