See topic.
Currently, I have just become Harbinger of the Companions; yet I read that even Kodlak's room is not "secure" (even after I become Harbinger!) and those chests and cupboards respawn.
I don't mind trekking back to Riverwood (or near it) if there is a secure location to store my inventory there.
Near Riverwood? Anise's Cabin, located directly across the steam from the Guardian Stones. You'll be trespassing every time you go in the basement but - besides the barrel upstairs - every container is perfectly safe to store stuff in. It even has an alchemy lab and enchanting table. Just make your way to the cabin and enter her basement (quit it! You lot have filthy minds!!). As soon as you exit, she'll be hostile. Killing her won't get you a bounty as she attacks first. Good aligned characters need not worry too much about taking an innocent life. Trust me, she isn't the kindly old lady she first appears to be...
I've currently got all my stuff in that "safe" cupboard in Kodlak's room with the Daedra Heart on the plate sitting on top of it.
I still empty and replace everything regularly, though.
I am looking to buy Proudspire in Solitude (for that Stone of Barenziah!) and store stuff there!
Sadly, I've downloaded the latest patches - buying the manor is the only way I can get it...