My daughter has been out of nappies since she was 22 months old. She suddenlt self trained and i wasnt even ready!
Now at 2.6 she hasnt wore a nappy to bed for a month, she just refused to wear one or if i forced it on she took it off as soon as id gone! she is dry nearly every night, she goes to bed at 7pm and is usually up around 7am, I dont lift her and ocassionally she wakes for a wee so i take her and she just goes back to sleep.
She has about 1 wet night per week which i dont mind as i think shes doing really well.
I have heard horror stories of children that train young then have bad regression.