Then I received this comment from a reader:
We still use one for our 3.5 year old. Granted, it is mostly because her room is up, and ours is down, but still. She sttn great for the longest, then around age 3 started to get scared of the dark, bad wolves, bad guys, monsters, etc, etc, etc. So she started waking up at all hours. You just never know when or why they could wake up in the middle of the night. What if they throw up? Super high fever? Fall out of bed (when they are a little older, obviously!). I don't think it is about sttn, it is just about being able to hear them easily. If the child's room is in close earshot, then a monitor isn't really necessary. All of this is just my opinion!