Quote from thstart:
SSD disks right now are reported to deteriorate with time and the access time to increase after usage. It is still not clear why but this info is not popularized. They still expensive and indeed storage logic is half of the story.
Decent article here that discusses the issues:
http://www.anandtech.com/storage/showdoc.aspx?i=3531
The ageing problem is mostly with writes and is highly dependent on the controller chip and firmware used in the drive. The forthcoming ATA TRIM command already supported by some new drives will also mitigate the problem. Linux kernel filesystem/block device support for TRIM will be out very soon. Windows 7 will support it sometime in the future.
