OK, don't laugh, it wasn't my idea I just inheirted it.
The company I work at is still using ACAD 2000.
The drawings are simple and only have about a dozen layers. A finished drawing is maybe around 600KB. There is one user whose files consistently are 3 and 4MB. I've tried purging them, using superpurge, wblocking into another new drawing file and auditing them. Nothing works. One interesting note, when I ran the audit on one of them the first 2 passes it found 1067 items, the 3rd pass it found 20,700. I don't know what's going on.