4 month old has been waking up from naps after 30 min since she was 2.5 months old. I use to rock her back to sleep and hold her to extend the nap. However, the bigger she gets the more difficult this has become and I will end up holding her for naps for half the day. Should I continue to rock her to extend the nap or let her get up when she wakes? She only wakes up once to eat at night and usually does great.