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).