There is a whole community of bag enthusiasts who intricately review backpacks. Packhacker etc. It's super easy to find reviews of most backpacks and plenty of video reviews detailing every feature on the bag - and even in some cases reviews after a few months of usage. Day one might feel great, but after a few trips you start noticing flaws.

I'd echo what one of the other commenters here said about AER and Cotopaxi. Although I have to say wearing my Cotopaxi Alppa 35l feels like a small child is trying to drag me to the floor compared to the comfort of having the AER straps on my back for the travel pack. I still love both though.

Aer is sort of an interesting case to me. At its core the nylon material they use certainly make the bags feel like they'd last forever.

But I feel like Aer also tends to include features or materials that are just not designed for BIFL longevity. Two that jump to mind are the PU coatings on a lot of their zippers and their use of elastic straps as the main way to secure water bottles (but they might be moving away from the elastic on their newest bags). Both of those feel like they have a much more limited lifespan (relative to some of the other aspects of the bags).