This refill lasts me about 1.5-2 months of daily usage. The Zebra G-301 pen is
great, and I use it every single day at the office as my "bullet journal" pen.
These refills are what really make it a winner. Like most gel refills, they
don't last long, but unlike many gel refills (looking at you Hi Tec C) they are
reliable, and you can use them until every single drop of ink is gone. I've been
using these pens daily for almost a year now and I have yet to meet a dud.