I really like DOE clearance upgrades and re-investigations. DOE has a firm grasp on the security program.
The 8 1/2 hour ESI was an SSBI where the Subject just wanted to argue every point (he was not getting a clearance… the Army put him in for a TS just 6 months after he was denied a Secret) and, of course, everything was a conspiracy against him.
The 6 to 6 1/2 hour ESIs almost always involve finances with developed foreign issues (citizenship).
My current average ESI is probably 60 to 75 minutes. Sixty or less on “clean” cases.