What causes tap cartridges to leak?

thor

Does anyone have a clue what causes tap cartridges to leak?
I had a mixer tap which began to leak just over a year ago and decided to replace the whole tap. The new tap then began to leak after just a few months and as I could not afford to shell out so much for another replacement so soon I decided I had better find out if I could repair the tap myself. So after doing a bit or reading I discovered this could be done by changing the tap cartridge. I found a new one and proceeded to put in in myself. This has worked for about 4 months but now it is starting to leak again.
The upshot of it all is that three cartridges have become faulty in a year. So I am wondering what kind of problems could be causing these cartridges to wear out so quickly. It can't be just bad luck can it?

frank.hopper

Is this a problem only with the cold side or both?

1984ReturnsForReal_2

air temperature

anotherbaldrick

Limescale, you must live in hard water are. Take the cartridge out of the tap and soak it in domestic limescale remover for 10 mins. Work it back and forth a few times. and it will work OK . I keep a couple of spare cartridges and just swap them over and then clean up the spare.

thor

The problem is just on the hot side.
I don't think hard water is a problem as I live in West Yorkshire which I believe is a soft water region.
I have looked at each of the faulty cartridges and have not seen any sign of wear and tear so am starting to doubt if they are the cause at all. It is just that I cannot see any other route for water to escape.