DD is 3 weeks, weighed 8lb 6oz at birth, lost 6oz of her birth weight but had shot up to 8lb 12oz by 1 week.
She feeds so quickly, feeds rarely last more than 5-10 minutes but she's still happy to go roughly 2-3 hours between feeds during the day and about 5 hours during the night. It seems to be working for her, she's gaining weight fine but I'm worried, with my other 2 I remember feeding for hours and hours.