I logged two of Peri's days at about 3.5 weeks, because that is when she was nursing constantly. I think it was time for her growth spurt. She basically would sleep only 20 minutes at a time, with an hour being the longest she would nap. She would nurse 45 minutes, then wait 15 minutes (just enough time for diaper change and a spit-up) and then go back to nursing. I counted up all of the naps and she did manage 14 hours a day! Of course, it's hard for ME to rest when she's doing this!!
She is 5 weeks today and while she will occasionally sleep 5-6 hours, her MO is to sleep 4 hours at a stretch at night, starting at 2 or 3am. Days when we have chiro appts are generally rotten days for her, but the next day she will sleep virtually all day, soundly.