Hi,
I use normal ink-liners. I use them in a normal fashion, but they keep on breaking on me, or get dry really fast. I used a wide range of brands, nothing seems to work.
The best brand I used so far, was Artline.
Which ink-pens do you use ? Can the tips be fixed ( they go into the pen, so that it is the metal edge I’m drawing with )
Thanks,
Jakob
Are you pushing too hard?
What kind of paper are you writing on? Different paper has different tooth (texture) to it, which can effect how long your pens last.
The regular old Bic seems to work wonders for me.
the expensive pens never seem to have the most life. Leave them for the tight renderings. I agree with Cyberdemon, Bic pens are cheap but react well to pressure change.
If you’re heavy handed, you’ll break tips. The best soft tip pen I’ve found is the Sharpie brand “PEN” It’s not a permanent marker, even though it says “sharpie” and has a soft tip that’s very durable. Very similar to the pilot razor point (which I burn through) Too bad it doesn’t come in a few different line weights. 
Thanks… Ill try the sharpie. I am heavy handed, I should try to easen up. I use normal copy paper, as well as normal sketching paper.