Secondarily.....when SSE comes out is it likely to provide longer, more stable saves.
Just as a measure I'm thinking....could you have a single character with let us say 1000 hours on it?
You're talking about save files in the tens of megabytes, running in gigabytes of memory.
The size of the save game should plateau because cell resets will let some content be deleted, and there's a finite amount of stuff to keep track of. After some point, there will be nothing left to add.
On PC, this doesn't quite work the same way, as the longer you play, the greater the temptation to add mods that have extra save requirements for the new content.