My daughter has sweated profusely when she's slept ever since she was a baby; she'll be 9 years old this month. She doesn't like hot or heavy PJs and will often wear shorts and a short-sleeve shirt to bed. I ask if she's cold, especially in the winter, but she insists she's always hot.
I've noticed that since she was diagnosed with heavy metal poisoning last Aug 2008 that as she's been chelating (taking medicine that helps her body get rid of the heavy metals), the amount of sweating she does at night has gone down. Drastically. She is to start a third round here in a week or so, and I'm hopeful after this one is finished, there will be virtually no smore weating. She literally used to sweat so much, it was as if someone washed her hair overnight!