Since you're kindly offering recommendations, what do you use for longevity in engineering notebooks?

If you want a low maintenance option, your best choice will be fade-proof pigment inked systems.

From top of my head:

    - UniBall Eye / Vision Elite's Red, Blue and Black (look for fade-proof / water-poof note, or SuperINK)
    - Sakura / Faber Castell / Rotring pigment inked, felt tip markers (Look for Archival Ink / Fade Resistant)

If you prefer fountain pens:

    - Pelikan 4001 blue black (which is not sold in the US)
    - Rohrer & Klinger's Iron Gall inks (scribosa, ebony, etc.)
    - Noodler's "Bulletproof" series cellulose reactive inks.
    - Lamy Blue Black
    - Lamy Crystal Benitonite
    - Montblanc Permanent Blue / Permanent Black

I'm sure there are many more, but these are the ones I know and had experience with.

Always use an acid-free higher quality paper. Leuchtturm 1917, Rhodia, Yu-Sari, Mnemosyne comes to my mind. Do NOT use Moleskine notebooks with fountain pens. They are not designed for fountain pens.

> Do NOT use Moleskine notebooks with fountain pens. They are not designed for fountain pens

Or for hard use in general. Well over priced for the quality of the paper and bindings.

What bothers me is, their notebooks were fine when they first came to market. I still have their old, filled notebooks with great bindings and paper, with spotless ink retention, incl. fountain pens.

They gradually reduced their quality, and created a “higher, more expensive tier” to offer their previous quality.

Leuchtturm 1917 is a world apart when compared to today’s Moleskine.

Unironically, my favourite is the standard Bic Cristal medium 1.0mm in black, but placed inside a Bic Round Stic body that I’ve reused for many years (I prefer a plain gripless thin body, since I use a gentle finger-leverage posture for applying pressure variations which I learned from the Palmer script method)

Or, for gel-based, the Uniball Signo black ink is my second choice. I particularly like using the Signo GelStick 0.7mm which I can make line variations from hairlines to super broad strokes (again, the leverage-based force application is key for effortless pressure variation techniques)

What's the timeline for this? My undergrad notes from ~15 years ago have held up without obvious degradation. Those are mostly Jetstream inks on generic paper (some Oxford notebook). I swapped to fountain pens at some point when I discovered Noodler's. Bernanke Blue dries extremely fast. Though my TWSBIs from the time haven't held up well. They were fine when constantly used but they cracked in storage.

It somewhat depends on the humidity and temperature. I have not tested for controls, but I suspect it has to do with the low-viscosity oil component undergoing some process similar to paper chromatography where upon contact with moisture it separates from the pigment seeps to the back of the page.