Mine stays on until I turn into a parking lot of some sort. Now that is on my truck with a cat in it. I can shift or coast without it activating when I want to. I have been driving a couple of cummins powered rigs and they are much more sensitive about coming on, so some what of a pain to leave them on, but a pain to shut them off too as a lot of my driving is in hills.
This is me. I've got a switch on the shifter, I'll flip it on when needed (gaining speed going down hill or coming to a stop), but leave it off the rest of the time.
Yes, Dear, That's Right Dear ... Jake's don't burn fuel when activated. Adept Ape talks about this in one of his videos.
Mine stay on assuming the roads are dry. Only turn them off in parking lots, city streets and residential or farming areas when running the two lanes. The day I need to worry about the .0001 mpg the Jake operating costs me is the day I realize I haven't the business sense to own a truck.
The theory is that you coast farther/longer with out the Jake on. It's correct. However its just like many other things, works on paper but offers no benefit in the real world.
In the five months I've been driving my truck I've never turned the engine brake off lol I utilize the heck out of my clutch shut-off switch
100% highway driving. Minus winter conditions. Don't need them any other time. I know some idiots that never turn em off. One guy. Will rev his engine when he's using his hydraulics. And let off the gas. VROOM. ROARRR. VROOM. ROAR. Always knew when he's around. You can hear his jakes inside the building. The you got the idiots bobtailing at the truckstop. Jakes work by shutting off fuel. That's taught in class. Or was. Stage 1 is 1 cylinder. Stage 2 is 2 cylinders. Stage 3 is 3 cylinders. That's also taught in class. I don't know how in the world you can coast farther with em on.
