1) Neal S. @ M-B USA (800) 222-0100 got the answers to the idle time questions straight from Germany and left me a voice mail:
With high idle option idle time is 1.5 to 2 hours. The rpm is programmable (if necessary) by dealer using "Century Diagnostics" (M-B proprietary equip., $22,000, for anyone considering DIY).
With stock idle, maximum idle time is one hour.
I just called and confirmed the above with Neal, to make sure I understood him correctly.
2) Mel Condon, shop foreman @ Sun Motors, Inc. said:
He would need the VIN to give an accurate quote but that they can do the high idle option.
There are two option codes from M-B -- one indicates that the Sprinter is pre-wired for the module, the other indicates that it has the module installed.
Mel said that if the cooling system is working properly, the Sprinter can idle indefinitely. Sun Motors has many customers with Sprinters who are contractors and let them idle for hours at a time and they've never seen any problems.
I told him what Neal had said about the idle time and Mel said that he would be going to M-B USA headquarters soon for training and would try to get the question of idle time settled.
3) Sheldon, service advisor @ Freightliner of Hagerstown gave me some (steep) prices for the high idle installation at their shop:
The Sprinter does not need to have cruise to have the high idle installed, but there are two sets of prices:
A) With M-B code EB5 -- $417.43
B) With M-B code EB8 -- $1,450.44(!)
A) With M-B code EB5 -- $588.60
B) With M-B code EB8 -- $1,621.61(!!)
Sheldon said again that with the high idle the Sprinter can idle indefinitely.
The safe bet at this point would be to assume that Neal has the right info. If that's the case, then I'm inclined not to bother with the high idle because that's a lot of money to spend for just 0.5-1 hour additional idling time.
I'm curious as to what Mel will find out -- I'm guessing he'll get the same answer Neal did.