I have files hat consist basically of a large grid, with artwork laid out on it. The artwork is all stored in symbols, and one instance of each is placed on the grid.
After some minor correction to one symbol and addition of a few new ones, I noticed that the size of the AI file had decreased from 340 MB to 220 MB. I extracted all the symbols from both collections to separate files. These files were all of similar sizes (but never exactly the same)
So what could be stored in over 100 MB of seemingly redundant file space?