how often should my baby eat?

My 11 week daughter all of a sudden started nursing less, maybe 4 or 5 times in 24 hours rather than her usual 7+ times. She nurses for the same amount as usual anywhere between 15-20 mins. She seems really happy and content and still has plenty of pee and poop diapers. Is it something I should be concerned about or maybe she is just more efficient at getting milk out? It literally happened over night and has been happening for just a few days!