Don't know about common, but I had a baby hoover too! DD would take up to an hour to feed for at least her first 8 weeks. DS could empty a boob in 5-10 minutes flat, from birth. He gained weight beautifully and had plenty of wet nappies so was clearly getting enough... just quickly! I guess that'll provide your answer - if she's gaining weight, she's just an efficient little feeder.

Congrats on getting BF established! Best and blessings for a beautiful feeding journey together. xo