History can prove tricky with InRoads.
Many displays are re-written that contain large amounts of data when a small area changes. A couple of edits to a DTM at different times will need re-display of the entire DTM each time. Move a PI and the alignment and its stationing all must be re-written. Revise the profile or cross sections - another re-write.
This can balloon up the size of the DGN file with history enabled.