The following is quoted for the BMW SC factory website (not BMWUSA).

"Production time
36 hours per vehicle
- Body Shop 4 hours
- Paint Shop 13 hours
- Assembly 19 hours"

BUT this assumes that your X5 goes directly from one step to the other. IOW the MINIMUM time for the SC factory to build an X5 is 36 hours. But many X5s pause between the Paint Shop and Assembly phase on what they call the "stacker". Mine waited on the stacker for several days.

"From here the finished, painted, and sealed body is conveyed overhead to the stacker to wait its turn for Assembly."

Once the Assembly is complete it only takes hours to get it over to the BMW Prep Center and ready for shipment inside the continental US.

Funf Dreisig