I have an electric compressor that I can run to get my coach up to 90 PSI. After that, its up to the engine compressor. The electric compressor takes about 15-20 minutes to air up to 90 PSI. From there, its just a couple minutes for the engine compressor to get it up to 110 PSI (where it runs).
I also have a high idle circuit. I wouldn't idle my coach at low idle - its not good for them. When I forget to turn on the electric compressor, I'll just start the engine and bring it up to pressure that way - with the high idle on.
I will also make sure that I let the turbo cool. But, I'll note that generally by the time I get to my spot, get it in to my camping spot, and drop the levelling jacks (which I do with the engine on), then I've had more than enough time to cool down the turbo.
Oh...and you won't find me idling my coach in a campground for 20 minutes at 5am. If I have to leave that early, I'll kick the compressor on at bedtime and have it where I can start the engine and go as fast as I can. By the time I am able to leave, the coach WILL be aired up.
