[Slydria]

Though answered, I figured it'd be appropriate to paste what I asked Dev directly about spirits here:

Is it possible to preserve a body for say, years?
What happens to a body after the soul leaves it?
Is it possible to return a spirit to their original body? If it is, is there a time limit on it?

Preserving a body for a long time can be done, just look at real life.

Spirits are a different problem entirely. Spirits don't leave a body until the body is dead. Once a spirit leaves the body, unless there are unique circumstances, it is pulled into Lazarus.

A spirit which is a special circumstance has almost no memory of their actual life outside of the circumstance that causes them to linger. A possession involving a spirit of a mortal would be simplistic and single minded. The only exceptions to this sort of thing are divine souls.

Once a spirit has left a body, that means the body is dead. The dead cannot be brought back to life, unless it's Mercala or something and she acts quickly.

Just look at Dullahans, they are essentially spirits tied to an object but they have no memory of their previous life for the most part and most of them follow a similar rule where they're just 'mad' and single-minded.