Standing in the Crib

My boys are amazing nappers. I spent 6 long months getting them to that point but it's paid off. But the last week has brought on a new phase... standing in the cribs. They can now pull themselves up but don't really know how to get down which is particuarly upsetting for Caleb. I spent the better part of an hour going in their rooms and continually laying them back down today. What is often a 2 hour nap on a good day became about 20 minutes where they were both asleep. From everything I've read it's just a phase and soon the novelty of standing will wear off. I have to admit though, it's pretty cute to walk in the room and see my two sons standing face to face, thoroughly enjoying each other's company.