I get asked all the time what the weight limit is of my packs and it's a hard question to answer. It's not the pack that's really the limiting factor but how you feel carrying weight, the terrain, what you're wearing and even the weather all play roles in what weight is comfortable to carry in a pack.
The pack shouldn't fail if treated right with any reusable load. That means not picking up a pack weighing 30kg by the shoulder strap, side strap or top strap. The lifter handle between the shoulder straps is there for that reason and that is for picking up the loaded pack. When my pack gets into the high 20s I find it easier to put the pack on while sitting down and then get up slowly.
I've had well over 30kg in my own pack a lot and it's got the std 12mm stays. But if you plan on carrying heavy loads (25kg+) then it's worth the little extra weight for upgrading to the 25mm frame. This just helps stiffen the pack and means you're less likely to bend the aluminum stays and also has a beefier webbing to house the stays.
For the sake of putting a number on the load rating I'd say max of 25kg. That's mostly just because I feel most people would find that weight comfortable in one of my framed packs. But I know people have had well over that in my framed packs with no problems. Such as this pack below with almost 50kg on the way out of a hunting trip and my own pack with 36kg. I feel that's way more then any lightweight pack should be carrying but It holds together just fine.
