Yvette, I'm no expert and certainly don't have twins, but my SIL has twin girls and her theory overnight was one up all up. There was no point feeding one, getting back to bed to sleep and then the other one waking. (I'm sorry I don't know how long she did this for, and I can ask her if you like and get back to you.)

That being said... If Lauren is sleeping through on a regular basis, I'd be letting her sleep.