I just found out about the seven chests/containers near your arrival spot in Shivering Isles, but they don't seem to reset every three days, I'm thinking it takes a bit longer. Rockmilk Cave usually nets me a ton of cash (mostly from the Daedric stuff, not many impressive rares there at my level, 44) and a chest hidden on a sunken Aeylid ruin on the West side of the map in the sea. I hit the two boss chests in the sewer system by the Imperial City also. Have you found any particular boss chests that usually have something good, or any favorite caves or ruins aside from the main ones we all hit up (Robber's Glen, Rockmilk, etc)? --- 'Now I stand here, waiting.'-New Order, Blue Monday (The Beach)
I usually hit up the trapdoor entrance to Ceyatatar every three days. Even if you haven't explored this ruin, you still have access to one boss level cask inside the tunnel.
The thing I like most about this location is, the chest is just inside the entrance so you can save your game right outside the trapdoor, go inside and inspect the cask and if it isn't anything you like, just re-load and repeat until you get something you do want. --- Hey you, yes YOU! If you're not going to answer the posted question, then don't bother to reply!