It was 1.5 hours for a long time, but she is starting to change and sometimes goes for 2-3 hours before her next nap. She take 4-5 30-45 minute naps a day. I go by her cues, but it is somewhat of a routine (as in I can usually guess when she will be ready for her next nap). A couple times in the last few days she slept her 30 minutes and woke up grumpy. I put her back to sleep and she went for another 45 minutes, so maybe longer naps are in our future? She is happy between naps, so I just go with the flow.