I have an older Class A gasser and to be honest I don't try to idle long with it, however if I'm getting set up, I need the engine on to run my jacks. Once I'm level I'll shut it down. When getting ready to leave, it kind of depends on the time of year. In the summer I will pretty much fold everything up and disconnect with the engine off and only start up when I'm ready to pull up my jacks and head out. In the fall/winter or a really cold morning where I have to get going early, I'll start the engine a bit earlier to get a little bit of a warm up and get some dash heat going, but again, not more than 5 minutes of idling. Also note, I drop my jacks onto pads, so I have some in and out of the rig while the engine is running to set my jacks, and when I get ready to go, there is in and out again for the purpose of retrieving my pads. All of this while idling.
DPs have many more considerations, they are quite a bit more complex than a gasser, and diesels have different needs, notably air systems have to be charged up, exhaust and turbo temps are something that have to be considered, too, especially at shut down. Also, diesels run better when warm. Starting a diesel and driving away with it bone cold is generally not advisable unless you have no other choice and just have to go right now.
I think there are some out there that are excessive idlers, but everyone has their reasons and maybe we won't agree with it, but we can't change it either. Sorry to hear you are leaving the road, but everything has a time and place. Best wishes on settling down.