We seperated at night around 5 months (they were rolling over onto each other and waking each other up all the time). We stopped having them nap together around 7 months. They always seemed to go down for naps better together and since naps are shorter, I didn't mind so much when they woke each other up. Now they are completely seperate and doing fine. THey still go in each other's cribs every now and again for some play time (which sometimes turns into cuddle time... awww). It's tough to do it at first, but you'll see that they will actually sleep better on their own
6 months. Even though it was sad to split them up, they totally slept better afterwards and (now that they are crawling and pulling up) they always creep over close to the other one's crib and babble/play together. It it adorable. We have the two cribs next to eachother along the back wall.
Re: When did you separate to 2 cribs?
We separated at 5 weeks when we started putting them in their cribs. Natalie can roll and Audrey can scoot, plus their crying wakes each other up.