Yeah, simons12 is right about that sucking the life out of it. It's not just bricks either, anything porous will wreck your mix if it's thirsty. I see it like leaving a door open - you're just asking for a weak spot. In my line of work, that's how pests get in, through the gaps you didn't mean to make. A solid bond is a solid bond, whether it's mortar or anything else.