I've got a 5 month old girl who lately has beco...

I've got a 5 month old girl who lately has become a serial snacker!! She is breasfed, and will feed about every hour (will go a little longer if she sleeps) but only feed for about 5-10minutes. Does this happen to anyone else? Sometimes I give her a bottle of formula just so I know she is getting a good full feed. The weird thing though is it's only during the day. She will sleep for 10-12 hours at night without waking. Am I the only one out there with a serial snacker?