I haven't bought a house, but I have my own quarters as:
the Archmage of Winterhold, after Savos Aren dies and I bring back the Staff of Magnus.
If I put some items in a chest by the bed, will they stay there permanently until I remove them, or could they be stolen by NPCs, disappear over time, etc.?
On a related note, I've noticed that items remain until I come back when dropped arbitrarily across landscape, buildings, and caves. Has anyone experienced a case where this is not true?