pete, no doubt vanguard is a grafter, so are many on here but if you have ever cleaned a lot of chairs in one go you will know how tiring it is, not only that but you just cannot clean a dirty seat properly in 30 seconds even if it's a 'bum only' seat, it will take longer than 30 seconds to extract properly, if the chairs are very clean anyway, you might just get away with it. also the ligistics of a large job like that would take time.
colin