I stashed some stuff in a barrel in Gerdur's house on my first playthrough, nothing disappeared (though I dunno how long I left it) but everything worth over about 60 septims was flagged as stolen when I took it out, so I couldn't sell it. I try not to hold on to too much at the start, if I can't disenchant it or use it right now, I sell it. There's so much stuff to loot/buy that I've only once or twice got rid of a couple of things that I sort of wished I hadn't later. My first character I hoarded terribly (and didn't really have a follower to carry it) until I got the 5k for Breezehome (which took me a couple of weeks game time because I couldn't carry much loot). Once I was able to stash the things I wanted to keep, I made back my 5k within about three or four days in-game because I had so much more carrying capacity.