My oldest went to a toddler bed at 2 years old, and each of my two younger ones went in at 20 months. The transition was much easier at 20 months than 2. I should say that independent sleeping is very important in our family, and so we never co-slept with our children. They slept in our room as infants, but never in our bed. Consequently, we never have our children try to crawl into our bed at night, they much prefer their own beds. I mention this because if your child really likes to sleep in your bed, you may have a frequent visitor once he can be more mobile.