The quote is from the internetwebz AI so it must be true!![]()
Problem with the game is one person might be able to leave stuff somewhere the whole game and it never disappears, someone else might have it disappear the moment their back is turned. You can do certain tests with renamed items in containers but even that isn't foolproof. The only place that bugs aside should be certain is player owned houses.
You can do the Knights of the White Stallion quest fairly early on to get access to White Stallion Lodge and the open corn sack things in there "should" be safe but stuff left in other containers or on the ground in there might randomly be picked up by Mazoga though apparently if you don't talk to her again at the end of the quest to confirm she is a knight-errant then she never goes to the lodge.
Jauffre's chest at Weynon Priory should be safe as well as mechanically the game doesn't reset it.