Any jeans I've had that are actually made the same way they were in the early 20th century last. Levis on the other hand.
I just shopped at the Levi's store at the mall in San Jose, and the jeans I mentioned were hidden on bottom shelves under all of the horrible synthetic crap. The good stuff is there, you just have to look for it.
This. I get only the natural, non-stretch fabrics (Leviticus 19:19, FTW!) and mine typically last up to a decade or more with decent care (turning them inside out before washing, washing only when visibly soiled, etc.).
Now granted, this is also a problem now that I’m losing weight, as they’re too loose to use without a strong belt, but too good of a condition to justify replacing.
For what it's worth, I wear mostly pretty cheap American Eagle jeans with stretch and they have lasted years on me. And that's despite basically wearing only four pairs of them in heavy rotation.
A big part of it is that I don't wash them every time I wear them. If I don't do anything to get them actively dirty or sweaty, I'll wear them a few times before they go in the wash. My understanding is that washing machines are, by a very large margin, the largest source of wear in clothing.
...And the sodium percarbonate used as a stain remover in washing powders rots the fabric and also attacks the metal in zippers.