If baby is gaining weight normally and produces enough wet and dirty nappies, the duration she nurses should not be a concern.
How to keep baby awake:
-switching breasts when baby stops suckling actively and seems to be dozing off
-burping and changing diapers
-feeding in football hold
-breast compressions to help baby take in more milk
http://kellymom.com/mother2mother/sleepy-babies/
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