Keys Of the Keyboard

11 months ago – few keys cannot function on the MS curve 2000.
Replaced with a new one of the same type, and it lasted only 3 months with another set of keys unable to function.
Replaced with a new logitech keyboard, and after a few months, the same problem occured, with another different set of keys cannot work.
Replaced with an A4tech keyboard, and within a week, a few keys failed.

Any ideas?