Something that niggled at me about Oblivion (and to some extent Fallout 3) was 'Item Respawn'.
When I found out that items would 'reappear' (or randomise) in there container, and flowers/plants would regrow from there stem every three days or so, I would just keep coming back again and again and again, rotating different areas to maximise the loot 'harvesting'.
Now that was fine if you were a casual player, but I, like so many fellow ES invested hundreds of hours into the game and found that this respawn mechanism to be rather boring and repetitive. It destroyed some element of immersion since the respawning was predictable and felt artificial. You were Guaranteed to have an item there if you came back at the alloted time!
The problem is, is that I can't think of a more realistic option to put forward to deal with this issue short of getting rid of item respawning or together, I certainly wouldn't want to see that. Surely there must be a more practical way of 're-laying the table' without it being so predictable and artificial.... hmmmmm.
No respawning, very limited level scaling, multiple hundred hours gameplay.
Pick two of tree.
you will probably get 30 dungeons level 40-50, if we are real lucky we get around 50 high level ones.
No respawning and you have cleared them out you are done, yes you probably use some time fooling around doing level 20-30 dungeons getting more and more bored.
With no respawning you run out of stuff, Fallout 3 was pretty stupid here, outdoor enemies respawned but not their containers and not the base the guard was guarding. Worse you ended up farming hard to get stuff like gateling lasers as some outdoor locations had them but they was rare in random encounters.
Now the main problem in Oblivion was the strict three days away rule. For plants it should be a fixed time say a week, then if you are away some hours it regrows., yes it takes a year between harvests, however if you are gathering some places are earlier than others. A week sounds good.
In oblivion owning a farm was totally pointless you had to stay away to get new harvests.
For dungeons say 10-14 days away, yes if you take over a bandit lair and make it your home the bandits might come back if you are away for weeks.