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.
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.