How quickly I ran out of an ink pen

I've been doing the 0-second writing for more than 3 weeks now, and I'm surprised how much ink I've used.  I had so many unused pens that I got as a SWAG, but I can use all of them!  

I marked a black dot every day after the writing, so 2 dots indicate the amont of ink that I used by writing 10 sheets of paper.  I finished using this pen after 5 days.  Wow, writing uses so much ink, actually.