Epson (R200) Ink - ALWAYS down - need fix!

Hello.

I have an Epson R200 printer and, once in a blue moon, I print in colour (CDs and DVDs for bands).

On all other occasions, I choose to tick the "Black Ink Only" box (print preferences).

Despite this, all colours routinely show as having been used.

Their levels go down, when it should not be possible for them to.

I ought to have the same cartridges I used, three sets ago, but I do not.

This does not happen rapidly, but it is noticeable.

Is this an Epson bug or plot to get us to use more ink?

There must be some sort of hack / workaround, to fix this problem.

Please link me to what you know, as it would be most appreciated.

Thanks!