These high-sided, enclosed play areas are popular because they allow parents to put their baby down with the knowledge that their little one can’t wander off. However, playpens are no substitute for adult supervision — never leave a child unattended in a playpen.
Both my children have spent more than a few hours in our playpen in the first year of their lives. At the beginning it was just a nice place where they could lie and look at the mobile or play with the baby-gym. When they could sit it was a place where pillows and special toys were kept — a place to put them when I needed both my hands. When they started to crawl it became a safe place where they could also experiment with some new moves. Even when they were older than 12 months I put them in the playpen always surrounded by toys or books.