[wingnut60]

Bob,
I don't know much about newer brake systems--but I remember having older trucks/cars that might have had low fluid levels in the brake lines and required 'pumping' the brakes to work. Seems to me that you need to understand what make the brakes work and how that can 'lose' pressure when sitting for a long time. You seem to be able to let the truck sit for a long period--have you thought about letting it sit at your mechanics' shop and then trying to duplicate the problem?
Joe