Son Sleeps 13 Hours

My 19-month old son went to sleep at 5pm yesterday... and slept through until 6am this morning. He had a big day and was obviously exhausted. It's the first time he's done this, and it's the longest he's ever slept for. Unfortunately, I assumed that he was going to wake up in the early hours of the morning, so I went to sleep quite early in preparation. I didn't sleep that well because I was constantly expecting to wake up, so I never got into that good deep sleep state. Maybe next time.