Jumbo John,
Like I said earlier alot of equipment would have to be removed for that kind of clean which would mean alot of inpestions (some duplicates inspections) and testing afterwards, not to mention the problems that are uncovered. If the equipment has to be removed for other maintanence purposes thats fine but the cost of removing things on that magnitude just for a clean is not cost effective.
When I worked in heavy maintanence many years ago areas were always cleaned when equipment was removed but I'd imagine now with the competition these days only the areas that are to be inspected are cleaned.
And as we all know its money that does all the talking in this industry.