Cable releases don't last

[Gallopingphotog]

I have bought at least three cable releases, and after a few months, they don't seem to work anymore. I took one apart but couldn't really see anything wrong, like a loose wire. (These are the electronic type, not plunger for film camera.)
I have k100D and k10D if that matters.
I am on a really limited budget. Any suggestions as to what I can do to repair/make one last longer?