Japanese selvedge jeans are very durable but expensive. The fabric is made on traditional looms, sometimes the actual looms from 1950s and earlier (those are mostly wooden contraptions, which can be repaired and kept in working order indefinitely) and can be incredibly dense to the point when you can actually make new jeans stand on their own (only possible because jeans are starched during production, you are supposed to soak them before wearing). But even light-weight 10-12 oz selvedge denim is still on a different level from a department store jeans.

The problem with the most department store jeans, no matter the price, is that they use fabric made on high-speed wide looms. These looms use light and smooth thread so they can weave fast. The fabric comes out very light (because of the thin thread) and does not hold together quite well (because the fabric is held together by friction, reduced by the smoothness of the thread).

Of course, it makes no sense to buy expensive jeans for durability. $400 24oz jeans probably will last for 20-30 years but so will 10 pairs of $40 jeans from Target.

I wouldn't call myself a denimhead, but I have several pairs of selvedge denim jeans from good tailors, one with Japanese denim, one with Cone denim.

Thickness counts for durability, and you have choices. I'm not sure what durability is like for cotton blends (it's rarely more than 3-4% synthetic). I have doubts that mass-produced denim of similar weight is significantly more or less durable than denim from traditional looms. The only differences I can think of that would impact this would be staple length and chemicals used in processing. Pre-faded, bleached, or distressed denim will obviously be less durable.

20 years sounds high to me. I have jeans less than a year old already showing crotch wear. Granted, this is expected, and it can be repaired before it's an issue.

Of course, if a wide loom could weave the same thread a narrow loom could then the output would be the same. It does not happen for the reasons I explained above: you cannot really weave thick, neppy thread fast - the thread will break.

I love my raw denim jeans, and assume they're likely better at holding up - certainly moreso than general brands.

For work (if style is less of a concern), Duluth Trading makes pants that last an order of magnitude longer than carhartt.

A word to the wise though; while my raw denim jeans are several years old now and in good condition, you sounds like you're dramatically harder on your clothes than myself.

I cannot confirm this, but I have been told Dickies last at least as long as duluth.

I've had pretty good luck with ll bean jeans after I got tired of buying levi's all the time. I recommend their regular line, the premium line has weird pockets and don't seem as durable. They also offer flannel lined jeans if you live somewhere with cold.

Same here, I used to be a big Levi's guy back in the day but they've destroyed one of the great American brands. Total garbage now. You can get much better jeans these days for a comparable price.

Knee holes are a nice failure mode. My last three pairs of jeans have split open completely in the back while I was in public. (And I'm neither overweight nor particularly large in that region.)

My next jeans have been fine for a decade.

https://www.nextdirect.com/CountrySelect

They do look worn, but I don’t care.

Surprised no-one has mentioned Vollebak. Their clothes are (claimed to be) pretty indestructible. Ceramic t-shirts, kevlar hoodies, dynema jackets, ...

Bonus: At $~500 for a hoodie, you're likely to make sure you stay in a shape that will fit into the hoodie.

Sugarcane dungarees are your best bet, here.