It's not rambling...
Our agency issues cars to all troopers, MCE inspectors, mid-management (Sgt/Lt/Cpt) and most upper management. As such, each car is only driven by one person for 95%+ of it's service life. Until about 18 months ago, the average service life for our cars was 95-105k miles. However, after management realized that this was costing more money to repair the high mile cars than it was worth in new cars, the policy is now ~80k miles. Take home cars are cheaper to maintain, but initial cost is more since everyone gets a car versus a fleet of "X" cars for everyone.
As for hours, the new 2006 CV police impersonator and DCX cars have hour meters in them for the exact reason mentioned by CPD. Idle time is very hard on engines, esp. when it's hot, the air is on and the coolant is hotter than normal. Oil changes really need to be based on hours of idle and miles combined.