I can't. That's why I rotate through them pretty regularly. I stick with one for a week, and my frivolity (frilly-volity @tifosi @Dino944 ?) is that I have Pilot Iroshizuku inks that I like for each specific pen. For example, I almost always put the yama-budo ("crimson glory" - a lush red) in the Dorsal Fin v2 in Kuro-Tamenuri (black/red), and the asa-gao ("morning glory" - a light blue) in the Ascending Dragon in aka-tamenuri (red/black).