The storage facilities in MM6 are limited and tricky.
Backpacks are simply not quite enough for those of us who want to keep EVERYTHING that might possibly become useful, and insist on claiming all available treasure and loot, day or night.
Everything left on the ground, except bodies, is lost upon exiting the area. Stuff can be stored temporarily in chests and crates, but that will be lost, too, once the area respawns.
So a bunch of us got to talk about additional storage facilities in MM7. Carts, packmules, carriers, you name it. My final suggestion was to give the party their own castle to keep all the property safe, complete with guards and all kinds of services.
It was a great surprise when we discovered that the idea made it into the actual game, even spiced up with the Goblin infestation that had already pestered Castle Gobs, too! Of course, we had to work very hard to deserve its full use.