You have to disable Steam Cloud support in the game, and also in Steam.
- In the game, go to the options screen->gameplay and set Steam cloud
to off.
- In Steam, right-click Bioshock Infinite in your games list
and select Properties. Choose the Updates tab and uncheck 'Enable
Steam Cloud synchronization for Bioishock Infinite'.
After you have finished playing, exit from Steam and cut/paste the C:\Program Files (x86)\Steam\userdata\XXXX\8870\ folder somewhere safe. Copy/paste it back when you want to restore that particular save.
To the best of my understanding, from playing the game, there are no stealth elements to the game except for one part.
The enemies usually don't wait in one place guarding or patrolling and "waiting for you", but are attacking you in waves, and everyone knows where you are, even if you are hidden.
A great example, is that there are levels where you can "roam" free at the start, until you steal, fire a weapon or use a vigor (even without hurting any one) and immediately all the cops in the level will come to your location and attack you, even if you were in some room alone, they will attack you.
The only exception is near the end of the game (minor spoiler ahead):
where there is an enemy with a "search light", if you are in the light for a few seconds it will attack, if you are caught for less the the time needed, it'll continue as if it didn't see you. You can run, jump, fire and do whatever you want behind its back as long as you don't get caught in its light.
From my experience, it has no stealth elements at all.
There is one thing which is the detection range of mechanized enemies, turrets, Patriots and Zepplins. They have a detection range and even a detection delay. And there is gear that affects it (probably reduces the detection range). I wouldn't call it a stealth element, because mechanical enemies are seldom alone, and once a patriot or a turret sees you, it'll know where you are and fallow/fire suppression fire, even if you are hidden from sight. This can be counted as a stealth element, but it's a very small one.
Best Answer
There is certainly a limit to the number of corpses/lockboxes in an area. I am not aware of any way to increase this limit.
Corpses will automatically decay (regardless of method of death, although disintegration tends to produce a lockbox immediately) over time into lockboxes. The older corpses/boxes seem to disappear to make way for the newer ones, in my experience. They will disappear without having been looted.
The easiest place to test this is the combat sequence at the Good Time Club. It's a long engagement in a relatively small area, and there are a lot of enemies, with breaks between waves to explore a bit.
The first wave here has a Fireman enemy, and I didn't have time to go loot his corpse between waves. By the time I'd cleared the next wave of enemies, the corpse and lockbox had despawned. There were also several enemies that I took down at a distance whose bodies had disappeared by the time I had a chance to go to where they'd died.
Enemies also drop their weapons separately from their corpse/lockbox. These tend to despawn somewhat slower, but they will still despawn over time.
The "bigger" bad guys tend to drop better loot - things like 80% health kits and the like. If you have a moment, it pays to loot these guys ASAP.
There appears to be a limited amount of persistence when changing zones. Sometimes I can exit an area and then turn around and come back and still find some stuff lying around, but it tends to disappear quickly. There are also times when zones you've been to before change or are restocked with enemies, and this seems to reset/remove any corpses or lockboxes.