Done in 23 segments in 1 week on the pre-update ep2 engine. Timing starts when the HUD appears and ends when I hit the end game trigger in the corridor.
https://www.youtube.com/watch?v=W9be4SUCNyc
The main trick in this run is the ceoob and save/load skip at the 1 minute mark which skips ~2-3 minutes of indoors stuff.