Until the Tooth Fairy forgets.
What? The Tooth Fairy has never forgotten your children? You're telling me that the Tooth Fairy has never gotten a wee bit drowsy around 9:30PM, then passed out in front of TV till the next morning?
In my house the Tooth Fairy needs all the help she can get. When a tooth comes out, I immediately create a midnight "Tooth Fairy" appointment in Google Calendar with a text message alert. I charge my mobile phone on my nightstand, so it's sure to be nearby.
There's no way the Tooth Fairy's forgetting my kid.
What's your strategy when the Tooth Fairy forgets?
More: Hacks for the Tooth Fairy