Zion falls asleep during stories, and Lijah falls asleep nursing or listening to music, but most nights I need to leave Harvey's bedside while he's still awake—if for no other reason than my presence is too distracting to him to let him drift off. Not that he realizes that; lots of times he feels like he's wide awake, and expects to be so for some time. So every night—every night, he likes his routine—I tell him I'll check on him when I'm done with whatever evening chores I have in front of me. For the last six months or so he's asked how I'll know he's asleep, because he might just be closing his eyes for a second, and I tell him I'll know by his breathing. Which in actual fact is totally not necessary. I'll really know because I don't hear him complaining about something, because that boy can't stay in his bed at night for more than five minutes without finding some reason to call for us... unless he falls asleep in that time, as he does 19 evenings out of 20.
Actually, the above isn't totally true: I don't tell him I'll check on him, and I don't give him the answer about breathing. Anymore. I did for weeks, or maybe even months, but I'm not a patient enough parent to keep saying the same thing over and over again forever. And Harvey knows that, so he fills in my side of the conversation. Our current bedtime closing goes like this:
D: Goodnight, I love you.
H: What are you going to do out of my bed before you come check on me?
D: Put away the bikes, close up the chickens, see if Mama needs help with the cleaning. Maybe do some writing.
H: When you come check on me, How will you know I'm asleep? Will you listen to my breathing to see if I'm asleep?
D: Yes. Goodnight, I love you.
I think it works pretty well.