TMT Poor you. It really wears you out, doesn't it?
Does Jemima feed well when she feeds? Or is it just a quick on-off thing, or does she fall asleep on the breast?
My midwife friend, who I trust implicitly, said that basically, a baby should have a good feed, until they feel sated, and then not ask for more for at least 90 minutes. Otherwise something is not quite right and there might be something else going on, not just hunger.
That said, when we were weaning Ianto of his bottles, I was constantly feeding him. He didn't take much from the breast because he was expecting the bottle, didn't get it, so wanted more after 30 minutes.
Also, we found out that with Ianto, we can't (or couldn't) quite trust the whole 'when baby is hungry he/she will let you know, he/she will drink as much as they need, etc' philosophy. We had to properly cajole Ianto into feeding. He would go on, take a few gulps, and fall asleep. Or go on, take a few gulps, and start to scream. I initially thought this must mean he wasn't hungry (but why then did he keep screaming for more?) but actually he was starving, but didn't have enough energy to feed, because he wasn't well.
Anyway, what I mean to say is, going back to the start of this post, if Jemima doesn't feed well, do you try cajoling her into having more? Like, preventing her from falling asleep, 'speed-breast-switching', keeping her on even though she is taking an extended break, feeding her naked, both of you naked, ... We had dozens of strategies and I'd be glad to share, just shout if you want to hear more. In any case, for us this led to a happier baby and less constant feeding.
As for a timeframe, I can hardly remember how it was for me! Somehow, it is just the good times that stick in my memory. All I know is that now Ianto is a bundle of joy :)