You and the Mrs are going to have to take turns getting a solid 8-10 hours of sleep every now and then, Jeff. Each of you take turns getting a GREAT night of sleep, far enough away not to be awaken by the baby. Either that, or if you're lucky enough to have a sibling, parent, or friend that can take care of the baby one night a week to let you both crash for 8-10 hours at the same time.... somehow you both have to get solid sleep at least once a week, preferably more often. You're right, only 5 hours of sleep is okay for one or two nights but not for longer.
