There is no strict rule about volume to feed if you are giving ebm since every mummy breast milk has different calories count and baby drink base on total calories daily. As a general rule most baby take between 700ml to 1 litre per day. Its okay if your baby drinks a lot she is at a stage where she need to grow. As for latching for 1 hr plus she might be just confort nursing. Its up to you whether you wanna let it go on or unlatch her.