I have been using the same ink Cartridge for two and a half years. I have to refil it about twice a week. I buy the kits for refilling from a local supermarket. I've refilled my cartridges this way for 5 years. this saves me over £200 per year.

You have to bore a little hole in the top of the cartridge to get your syringe needle into it.

Some cartridges have a layer of jelly stuff on top of the ink sponge inside the cartridge. This is to prevent refilling. SImply poke a hole through and away you go.

Don't wait until the cartridge dries up before you refill it.

Once you have filled your cartridge, remove a little bit of the ink. and put it back in the bottle. This seems to prevent over filling.

Never tried the colour cartridges though.

I only use black. But I have used fountain pen ink in the thing. And it works.