Eating schedule...

Kb103109

My twins are almost 7 weeks old and right now we wake them up every 3 hours to feed them during the day.  After their 7/8 pm feedings we wait until 11pm and 12am to feed them and then again at 4/5am, then back to every 3 hours.  Should I still be waking them up every 3 hours during the day and every 4-5 hours during the night??  Or should I be letting them just sleep until they wake up??  If I let them sleep should I feed them a little more at each feeding?  What did you do?  How did you know when you could space out the feedings more?