OK, so we now that placing stuff in dungeon chests is a bad idea because they reset, or respawn, or something. However, if I find a valuable but heavy item that would place me over my encumbrance level, would I be safe to just leave it there for a future return visit?

Possibly...unless the dungeon ''resets''.... ie: bandits or whatever go back in there, and the items re-spawn (potions, food etc), i think it would be still there, but not 100%

word of advice....unless you own the container, i.e. it's in your owned house, don't trust it.

I agree, but I'm wondering if it holds its "natural" contents given that I'm not actually changing it at all, other than peeking into it.

Well why dont you just try it??? save game at the chest (if you really want the item)

Then go outside, fast travel to a city and wait a month... basically wait for 24 hours 30 times..... i believe this is when cells reset. Then go back to said chest and see if it is there.

If you leave and return before the dungeon resets, it will still be there.
They reset in about a month.

I'm not 100% sure but it seems to me that leaving the item on the floor where you are is safer than putting it in a chest. I once killed some Thalmor on a road once; I didn't want to be encumbered so I left their weapons on the spot. When I came back, the corpses had disappeared but the weapons were still there. Something worth trying maybe?

From my experience as long as you dont wait more then 30 days(which is the time required for a dungeon reset) its safe to put stuff in containers. What I did during my first playthru was to kiting mobs to entrance to kill and place extra loot on them. Dead are containers too. But I would keep away placing loots on story mode dungeons.

To answer OP, yes, it is going to still be there.....for awhile.

Original items will still be there, allowing you to go back and dump loot, go back and get the rest. I have done this many many times. If you delay for a 'long' time though, it will indeed 'respawn' including new mobs and also refilling the chests. =) I used this alot as an ATM in FO3, Oblivion, and now in Skyrim. I had a couple of favorite badguy spots that I would hit every week or so(game time) as long as I was in need of ammo/coin/XP/etc.

A caution though...be careful adding items. They will still be there for a quick trip to sell, but they seem to despawn faster then original items. I have tested this by adding heavy loot to my holder(the first body or chest closest to the door). I then continued on through the instance, and generally the stuff is still there, but there have been a few times where the instance had several zones(when you pass through a door for example and it loads into the next section) and by the time I got back to the front end it had despawned although the original stuff was still there.
Hope this helped!

PS: Odd thing tho', the chests almost always don't relock....but they DO refill. Saves on picks I guess! =)

Thanks for the replies guys. I'm going to make the assumption that items are there for 30 ingame days after discovery. That is plenty of time.

A tip so you don't need to worry about this so much....

There are a lot of items that increase your carrying capacity. Once you find one, disenchant it, and then re-enchant a ring and a necklace with some grand soul gems. Weighing in at 0.5 but giving a +20 boost is worth hanging on to, and can help you out a lot in a bind. I found some boots that gave +40 and only weigh 2, those are great as well, since 20 seems to be the highest I can get this to at the moment making them myself. The potions are nice and all too, but the temporary effect means you need to have a bunch if you plan on finishing the dungeon you're in before returning to town, so these other items are a great help. Potions are nice though since they're lightweight, I just use them right when I'm ready to travel to town and sell stuff. Also, find the Steed stone, it's to the west of Solitude, and gives +100 carrying capacity. Or, invest in pick pocketing for the +100 carrying capacity perk. I find all this stuff worthwhile, because it saves me so much time with the whole item management thing. Followers work great too as pack mules - I tend to hate that they get in my way during fights, so I just have one of the Housecarls follow me until I fill them up, and then send them home so they're waiting at my house with my stuff when I get back.

And like others said, it should be a month before the dungeons reset. There seems to be some bugs preventing them from resetting properly, so some dungeons you can probably leave stuff there forever, but who wants to risk that?