Altura is renowned for making bike-mounted bags that last, and my experience of them fits that description exactly. The pannier bags pictured here are around ten years old, and are regularly filled to bursting like this for twice-weekly food shopping, beach trips and more.
So far, nothing has failed. The pannier rack mounts are as solid as the day they were bought, the rubber carry handles withstand the 15kg loads and show no signs of perishing, the bag clips, shoulder straps and pull-cords function perfectly, and the bags themselves (and the dry liners) are free of wear. In fact the only sign of ageing is a small presence of mould spots, but we have occasionally been lax with getting them dry after using them in bad weather.
We recently bought a second, smaller pair of Altura bags that are more suited to commuting, and expect these to last fifteen years or more. They're not cheap bags, but are extremely good value in the long term.
Here is another set of Altura bags in action, used by someone I passed on the road the other day. You can also see an Altura box mounted on top of the pannier rack.