Short feedings

Bekkers

DD is one week old. I started BFing within about half an hour of birth, and she has had a pretty good latch right from the start (the lactation consultant at the hospital checked on us a couple times). During the first few days, when it was all colostrum, she was feeding for a long time (half hour per feeding, average). Now that my milk has come in, she is having much shorter but more frequent feedings. I think her latch still looks good, but it's hard to tell. Is this normal? I figure she's getting way more to eat with the milk, but she's hungry ever hour and 1/2 to two hours (sometimes even sooner!). She is gaining weight, btw. Please let me know if this is something you have seen or if you think I should call my doc. Thanks!