I don't have twins, but I must disagree with the "never wake a sleeping baby" rule of thumb. Both of my babies were sleepy babies: they had mild jaundice, which made them sleep for hours and hours on end. I often had to wake them to feed them on a regular schedule until they grew out of the jaundice and developed their own stronger appetites. In addition to worrying about their intake, output, growth, jaundice, keeping them awake while eating, and trying to get some sleep at night myself, I had a well-intentioned MIL telling me to let them sleep! Go with your gut, and what works for you, but remember there are no "rules" in parenting - except to go with your instinct and do what's right for YOU.