When carried out with care and due diligence, can be benificial.
HOWEVER when NO care is applied, they lead to all sorts of complications. This was the case in the Red Section this week. Somehow, the cards from one board were substituted with the cards of another board; thus giving rise to the problems of having TWO KINGS OF SPADES in the same board !!
So please be CAREFUL; and remember that North is responsible for the safety of the boards in their possession.