My ID twin girls are now 16 weeks old, and generally seem to be fairly placid babies (I also have a 2 yr old DD who I remember crying a lot more)! We manage to get them into bed for around 7pm, and they settle down fairly easily. I'm waking them for a feed at around 10pm, then they wake at least once more in the night (anywhere between 2-5am,so I don't think it is habit). I did try not waking them at 10, but they woke up around midnight -and just as I was getting into a deep sleep, and still another 1-2 times.
I didn't think that we were doing too badly, but met a foster mum today who is currently looking after 2 babies, both of whom have slept through the night from about 6 weeks!! She looked in horror when I told her about our sleeping patterns! 
I'm currently bfing, although really starting to struggle with very sore nipples. Also I was tandem feeding until a few weeks ago, when they became too big to handle together. And they have between 6-8 feeds a day.
I read on another post about caffine and bfing (although I don't think I have that much tea and coffee, and without it would really struggle to keep awake all day!)
Does anyone have any advice on how to improve their sleeping at night? Thank you :)