Chaco sandals are generally fairly durable and a good buy from a longevity standpoint. They have many variants, but of the standard sandals, there are 3 components: an outsole, a midsole, and the webbing.
The outsole is usually rubber, and I’ve heard conflicting info on the durability of the chaco branded outsoles vs the vibram outsoles that are also available, but i can’t comment on that personally because my chaco branded ones have seemed fine. The outsole is something that will slowly wear down, but it is replaceable through the company (and independent cobblers).
The webbing is polyester, which is strong, soft, and UV resistant, but it can eventually wear through. The webbing is also repair/replaceable through the company.
The midsole, however, is not repair/replaceable (ship of theseus problem). The “classic” chaco midsole is a hefty chunk of polyurethane that is very durable. I know people with them that have had them for over 15 years, wearing them throughout the warm half of the year, replacing the outsole multiple times, and really putting them through the wringer. The “cloud” midsole, however, is designed to be more comfortable out the the box. It’s mainly made of the same polyurethane, but it has a 5 mm layer of a softer, blown polyurethane on top. Polyurethane can suffer from hydrolysis, where it breaks down over time, but the “classic” chaco soles are dense enough that it’s not a problem. The softer polyurethane is far more susceptible, and once it wears down enough to open up pores in the foam, it accelerates due to moisture getting trapped in the pores.
My cloud chacos started getting porous after 3 years of ownership, and basically unwearable after 4 years. The breakdown of the material combined with the moisture retention means that they stink so badly, I cant even keep them in the house. I will likely have to dispose of them if I cannot find a way to smoothly remove that whole layer of polyurethane.
I will also note that this can also be an issue with some boots such as blundstones that are built from the same material. Allegedly, making sure to wear shoes that have this material can help to extend life by driving out any moisture that has worked it’s way inside, though i cannot verify this.
TL;DR, be wary of any polyurethane shoes, particularly if they are soft/squishy