Out of boredom and partially to see if i didnt overlooked anything i spend the last 8 hours revisiting areas i havent visited since i started skyrim.
As i am now close to 90 hours into the game and close to 250 ingame days i was wondering what was still left in old previously visited caverns and villages.
Heres a sum of what i found.

Quest-related npc enemies wont go away in most cases. their corpses where still exactly where i left them, either fully stripped or with some leftover spoils.
(Besides potions and ingredients i never pick up items that arent at least ten times worth their weight so i can easily tell if the inventory of the npc was about the same.)

Almost all locations i visited in the 8 hours (areas i havent been to for at least 50 hours) not only had the npc enemies still dead on the floors, but most of the random items spread throughout locations all stayed on the exact same location all that time.
(Imagine all those hundreds of thousands of items and npcs with inventories being saved)

Almost every enemy i brought back to life (did this with whole dungeons to raise my skills) Turns to ash. These ashpiles dont seem to go away even after more than 60 hours/many seasons.

A dragon skeleton of the 2nd dragon i slayed is still where i left him though now partially sticking through a wall resulting in a lot of physic stress/stretching.

Riverwood is one of my least visited villages and the crate i used when i first visited the village (first 4 hours into the game) still holds all the items i dropped in.
The riverwood merchant is still selling the items i sold him at least 70 hours ago.

Almost all merchants beside the mages in the jarl buildings / alchemy selling npcs and the blacksmith using the skyforge still sell many items i sold em many many hours ago.

There have been houses i totally messed up with the unrelentless voice, all of the ones i could find still have all their interiors messed up.

Bearclaw traps reset moment you exit the location they are in.

Some of the npc corpses had new inventories meaning i could re-loot them for items but more importantly quest items where also re-obtainable.

A few locations do reset their interior the moment you leave the location, mostly where silver hand members are/where present.
One room was filled with iron ores and just going in and out of the stronghold resulted in an infinite supply of iron ores.

Selling all my 5000 weight worth of items/potions/weapons to one shopowner made my savegame go from 8mb to 10mb.

Smaller inside locations almost have no framerate issues even after 8 hours into the game, outside locations/cities where almost a slideshow though. (I expected crashes but they didnt occur this time).

When i did walk outside i noticed a lot of textures not rendering, backdrop did not load and one time the sky turned pale white till it all got loaded in again.
Running made things even worse and occasionally gave me 1 frame every 4 or 5 seconds.

For some reason when walking towards whiterun a dead draught fell from the sky. :/

Whiterun is one of the most laggy of cities.

Its almost 5am now, forgive me if i forgot anything or left in any typos.
Gnight

Oh just for beths sake:
Completed 5 main quests, 25 side quests.
(Been exploring more than doing quests)
My savegame atm is 9763kb

That's interesting that everything stayed where it was for you - I've seen the same thing. On a number of threads I've seen a suggestion that if you wait or sleep for 48 hours corpses and items will disappear but I've done that a number of times and whenever I go back to any dungeon or world map area I've previously been to it's always still in the same condition it was the last time I was there. There's still a dead wolf corpse just outside of Whiterun that has been there ever since I killed it like 20 game hours and several in-game months ago.

Interesting.

Sigh.. i reallly hate my phone and its stupid double posts.

I might do some more testing tonight, playing skyward sword with bro rest of the day.

Is it reproducible right after the start? If so the Bethesda-Staff should load your savefile and monitor with their tools what happens and why. Personally, I don't understand why they don't ask for corrupted/problematic savefiles, except they already know whats causing the issues.

Can the saves be copied (some have copy protection) if so... just send it across to them

They are the devs, thus they can surely adjust the protection mechanisms (at least for their dev-environment, which would be sufficient).