GoLite Odyssey Pack
This was reviewed as a round-the-world bag made from recycled fabric, and the reviewer's aside is the most durable thing in it: they could not imagine ever needing a pack that size.
GoLite is gone, at least as the company that made this. It went bankrupt in 2014, and the name has since been used by other owners for unrelated product. So treat this as a review of an idea rather than of a bag you can buy.
The idea was right and has become mainstream. Recycled fabrics are now standard across the outdoor industry rather than a selling point, and GoLite's other obsession, cutting weight by removing features, turned into the ultralight category that reshaped backpack design.
The reviewer's instinct was also right. Very large travel packs are a trap. They get filled, they cannot go in a cabin, and they make you a person who unpacks rather than a person who travels. For an open-ended trip, 40 to 50 litres carried is the size that experienced long-haul travellers converge on, and it is substantially smaller than what most people buy first.
What to look for instead: a front-loading travel pack in the 35 to 45 litre range that fits a cabin bin, with stowable straps and lockable zips. If you need more for a specific leg, a packable daypack adds 18 litres for 300g.
And on the sustainability question the original raised: the lowest-impact pack is the one you already own, because manufacturing dominates. Most good brands now repair rather than replace, which is the version of this argument that actually works.
Part of the guide to backpacks and daypacks.