@penfount I only have five pens. On the other hand, my memory isn't what it was, so it's a good thing three of them are demonstrators. The other two I occasionally need to unscrew and peer at, or try on a random bit of paper.

It probably helps that I don't often have two inks the same colour (although I did once get confused when I had both Diamine Monaco Red and a sample of Diamine Oxblood).