How old is too old for a baby monitor?

When I was pregnant, my mother-in-law gave us one of the best and most used baby items: a video baby monitor.  I can't imagine not having a video monitor!  It's helped countless times when she was an infant and woke up crying; we could instantly tell if she had a leg stuck or if she was okay and just needed a few minutes to get settled back to sleep.  At a glance, we could tell whether we needed to rush into her room or stay out and let her be.

My daughter is turning three in just a few weeks.  The other day, my husband looked at me and said, "You know eventually, we're going to have to stop using the monitor." 

My response?  "Um, no.  We'll use it even when she's 16 to keep the boys out.  We just have to get creative in hiding the camera."

I do realize that eventually, we'll have to give it up.  But for right now, when I don't think I could hear her call me if I have the fan on, or if I'm doing dishes with the water running, or if there is any other loud noise going on, I'm hesitant to not use it. 

When she wakes up, she'll usually lie in her bed for a while and then call out, "May I get out?" I'm not sure how I feel about giving her free roam of the house in the mornings before we're awake, not to mention the fact that sometimes she asks if she can get out when she hasn't actually fallen asleep yet, so I'm okay with her asking rather than just coming out of her own accord.  

But would I hear her ask to come out if I didn't have the monitor?  

Sometimes I can't wait for the day when she can come out and make herself a bowl of cereal.  Oh, to be able to sleep in again! 

Other days, I wish that she would never grow up and stay exactly the way she is right now. 

So tell me, what do you think is a good age (or stage) to give up the baby monitor? 

PS - If you haven't checked it out yet, go visit my new outfit diary blog, A Working Mom's Closet. Let me know what you think!